
FT MEADE 
GenCo11 












































Gass Q'cfrOS* 

Book__v A £ _ 

CcpightN 0 __ 'A , 

COPYRIGHT DEPOSIT. 



























































































































































































































































































*- 































































































. 














v» 








FERNS, FOSSILS AND FUEL 



TREE OF KNOWLEDGE 

UNIFORM WITH THIS VOLUME 



Percy Holmes Boynton 

THE CHALLENGE OF MODERN CRITICISM 

Tom Peete Cross 

HARPER AND BARD 

Robert Morss Lovett 

PREFACE TO FICTION 

Adolf Carl Noe 

FERNS, FOSSILS AND FUEL 

Louise Marie Spaeth 

MARRIAGE AND FAMILY LIFE AMONG STRANGE PEOPLES 

James Westfall Thompson 

THE LIVING PAST 












ADOLF CARL NOE 

ASSOCIATE PROFESSOR OF PALEOBOTANY THE UNIVERSITY OF CHICAGO 


V P V 

FERNS, FOSSILS AND 
*** FUEL 

THE STORY OF PLANT LIFE ON EARTH 

j 



THOMAS S. ROCKWELL COMPANY 

PUBLISHERS 1931 


CHICAGO 



Q£.^>05 

. Ns i 


COPYRIGHT, 1931, BY 
THOMAS S. ROCKWELL COMPANY 
CHICAGO 


J 


f> 

0 

0 • 
0 o 

00 a 




Printed in United States of America 


©CIA 


38366 di 



CONTENTS 


ONE 

Delving Into a Prehistoric Record 

13 

TWO 

The Classification of Fossil Plants 

28 

THREE 

The Beginnings of Plant Life 

50 


FOUR 

The Era of the Ferns 

60 


FIVE 

The Advent of Flowering Plants 

79 


SIX 


Plant Life in the Great Ice Age 

89 

SEVEN 

Plants and Man 

97 

EIGHT 

The Romance of Coal and Oil 

117 

Bibliography 

128 


The author wishes to express his 
indebtedness to Dr. Fredda Doris 
Reed and Mr. J. V. Nash for the 
help rendered in the preparation of 
this wor\. 


LIST OF ILLUSTRATIONS 


Page 

Plate I: 23 

Figure i. A coal ball from Southern Indiana, contain¬ 
ing a fossil seed (Trigonocarpus). Natural size. 

Figure 2. A section of a small stem out of a coal ball, 
showing the woody fibres. Magnified 75 times. 

Plate II: 37 

Branch of a Gingho, showing fan-shaped leaves. 

From Missouri Botanical Garden, St. Louis. One- 
tenth natural size. 

Plate III: 53 

Impressions of fossil ferns and fern allies from the 
Pennsylvanian. Natural size. 

Figure 1. A fern leaf (Sphenopteris). 

Figure 2. A fern leaf (Neuropteris). 

Figure 3. A fern leaf (Pecopteris). 

Figure 4. A branch of a horsetail (Calamites). 


Plate IV: 65 

Devonian landscape reconstructed in New Yor\ State 
Museum, Albany. 

Plate V: S3 

Landscape of Pennsylvanian age (after Potonie). 

Plate VI: 93 

Landscape of Triassic age, reconstructed in Stuttgart. 

Plate VII: HI 

Cycad tree (after Chamberlain). 

Plate VIII: 121 

Cross section through an oil field. 







FERNS, FOSSILS AND FUEL 







ONE 

DELVING INTO A PREHISTORIC RECORD 

K NOWLEDGE of what sort of vegetation covered 
the earth millions of years before man first appeared 
has reached an extraordinary accuracy. We now have 
information in this field which to many persons only a 
generation ago would have seemed unattainable. 

Just as we know much about the strange mammals 
and the incredibly gigantic reptiles—the long-extinct dino¬ 
saurs—that populated the earth in remote ages, so we 
now have a pretty good picture of the landscape amid 
which they lived; in other words, what kinds of trees 
and other plants surrounded them. The different varieties 
of plant life that flourished aeons ago, which great 
floods now and then buried where they grew, to be 
compressed and transformed into the coal we use today, 
are now so familiar to scientists that it is possible to 
reconstruct a whole forest of that period. The leaves 
and bark and seeds of the growing things can be repro¬ 
duced exactly as they were when this strange plant life 


13 



FERNS, FOSSILS AND FUEL 


covered the land in the distant prehistoric past. The only 
feature that we cannot be quite sure about is the color. 

We have learned what we know about the dinosaurs 
and other prehistoric animals from their bones and 
skeletons which have been preserved, in one way or 
another, in various parts of the world. The vegetation 
of former ages has left much the same sort of skeletal 
remains in botanical fossils. Such fossils are pieces of 
rock which bear the impression of a leaf or a stem, or 
even of a whole plant organism, embedded in them. 
They are a petrified record of something that lived during 
a previous geologic age. 

The science which is concerned with these fossil plant 
remains, with the arrangement of the fragments into the 
whole plant that actually grew, and with their classifica¬ 
tion, is called paleobotany, the science of ancient plant life. 
Its background is necessarily a combination of botany 
and geology, as the name implies, but it is much more 
than just a combination. The science is a comparatively 
new one; it is interesting to trace its development in the 
United States. 

When Louis Agassiz arrived in America in 1847 to 
take the chair of natural sciences in Harvard University, 
he had left behind him in the historic Swiss town of 
Neuchatel a man who had been closely connected with 


14 



DELVING INTO A PREHISTORIC RECORD 


him in his work at the local academy of sciences. The 
name of that man was Leo Lesquereux. In 1848, the 
Academy of Neuchatel passed out of existence and 
Lesquereux followed Agassiz to America. Here he 
introduced the study of fossil plants and became the 
father of paleobotany in the United States. He had been 
bom in Neuchatel in 1806 and was, therefore, forty-two 
years old when he came to this country, with his wife and 
five children, as a steerage passenger, arriving in Boston 
in September 1848. 

Lesquereux started with two severe handicaps. He was 
totally deaf and he had no money. Nevertheless 
America gave him the opportunity of his life. His first 
work in this country was done for Professor Agassiz. 
This consisted in working up and preparing for publi¬ 
cation the data on the notable collection of plants made 
by Agassiz on his Lake Superior expedition. The report 
was published before the end of 1848. 

At the close of the same year, he moved on to Colum¬ 
bus, Ohio, where he was to make his home for the 
remainder of his life. Lesquereux was called there by 
Mr. William S. Sullivant, a gentleman of large fortune, 
who was at that time the head of American bryologists, 
devoting his time and means to the science of mosses. 
Mr. Sullivant called Lesquereux to his aid, employed him 


15 



FERNS, FOSSILS AND FUEL 


for one or two years in bryologic work, and afterwards 
aided him in various ways in carrying on his paleobotanic 
investigations in the United States. 

The microscopic work connected with the bryologic 
studies affected Lesquereux’s eyes; so he turned to paleo¬ 
botany, which, at that time, did not require the use of 
a microscope. 

His first work on fossil plants was published in 1854, 
and from that time until the date of his death in October, 
1889, he wrote innumerable monographs and other 
papers on the fossil plants of North America for the 
United States Geological Survey and for the state sur¬ 
veys, especially the geological survey of Pennsylvania. 
The serial publications of almost all state surveys which 
deal with coal and coal-age fossils contain contributions 
by him. His extensive collections are now largely in 
Princeton University, together with his library. Many 
of his specimens are also in the Smithsonian Institution 
at Washington and a few of them are in the paleobotanic 
collections of the University of Chicago. 

A similar service, but under less difficult circumstances, 
was rendered to the paleobotany of Canada by Sir 
William Dawson, the late principal of McGill University. 

The basis from which these two men started was the 
life-work of Adolphe Brongniart, who had first treated 


16 



DELVING INTO A PREHISTORIC RECORD 


paleobotany on a scientific basis. He lived in Paris dur¬ 
ing the first half of the nineteenth century. In the middle 
years of that century, the study of fossil plants developed 
in England and in Germany, and became an important 
field of investigation there, as well as in France and in 
North America, gradually spreading to other countries, 
and enlisting the interest of more institutions of learning, 
until it became a well-established branch of botanical and 
geological research. 

The fossils from which paleobotanists learn about the 
plant forms of the geologic ages are found in various 
kinds of rock formations in all parts of the world. Slate, 
shale, and sandstone contain many plant deposits or 
fossils. These three kinds of rock are sedimentary for¬ 
mations. They were formed from material washed down 
from hills and mountains, and deposited in either fresh 
or salt water during some great inundation. These inun¬ 
dations were usually caused in geologic times by the 
movement of the earth’s crust, which caused the land to 
subside and be covered by the sea; or they were the 
products of slow, everyday processes of erosion by rain 
and water action. 

Slowly, changes in the earth’s crust were being carried 
on through all times. Eventually, there would be an 
upward movement, and the land which had been under 


17 



FERNS, FOSSILS AND FUEL 


water would rise again and the sea recede. The coarser 
sediment which had been washed down into the water 
formed sandstone; the finer mud, shale and slate. Lime¬ 
stone was made from the shells of water animals and from 
corals; ordinary limestone contains no plant fossils. 

Inundations were the primary agency in the making 
of such fossils. The plant materials were carried along 
in the flood waters and embedded in the mud, which 
hardened into shale, slate, or sandstone. Shale is the 
best material of the three in which to find fossils, because 
it is laminated, or formed in thin layers which are easily 
split apart. It is not so hard as slate, and its gray color 
makes it easier to see the plant impressions. The plant 
remains have been reduced by the terrific pressure of the 
rocks to a thin layer of carbon which shows very plainly 
on the gray shale background. Sandstone is too coarse 
to preserve many fossil impressions well. 

Excellent fossils are found also in volcanic tufa, which 
is the rock formed from volcanic ashes. Fossils embedded 
in this material are usually found in a place where there 
was once a lake with forests around it. Leaves and other 
plant organs drifted into the water and fine volcanic dust 
from some near-by volcano sifted over it. Finally the 
dust filled up and covered the lake entirely, forming in 
the process a sort of plant Pompeii. 


18 



DELVING INTO A PREHISTORIC RECORD 


The whole plant structure has sometimes been pre¬ 
served in a special kind of limestone, where the lime has 
been deposited by mineral springs and has entirely 
encrusted the leaves and the body of the plant. We can 
see the same sort of thing happen today at mineral springs 
like those at Carlsbad, where a small branch placed in 
the spring for half an hour or so will become completely 
encrusted with stone. 

In coal-seams, which are themselves vegetable matter 
tremendously compressed, carbonized, and changed in 
form, it is often possible to see, with the aid of a micro¬ 
scope, certain organs of the plants, especially spores, also 
woody fibers, resin drops, the epidermis of plants, and 
the outlines of leaves. 

A coal-seam is associated with fossils in the shale above 
it and in the fire-clay below it. The fire-clay is the soil 
of the swamp in which the plants of the coal age grew; 
the shale is the sedimentary mud which sealed up the 
coal seams from above, killing the plants but preserving 
their remains. 

Sometimes plants, and insects also, are found embedded 
in amber. Amber is formed from drops of the resin of 
coniferous trees which have fallen upon the blue clay 
and hardened there. Occasionally, a drop would fall on 
an insect or part of a plant and solidify around it. When 


19 



FERNS, FOSSILS AND FUEL 


this happened, a perfect preservation of the body enclosed 
in the drop resulted. 

Fossil plants are of two varieties; they are petrifacts, 
or they are casts and impressions. When the entire plant 
structure has been preserved, we call it a petrifact. The 
petrified forests of Arizona, where everything has been 
turned to stone, are a large scale example of petrifacts. 
The wood has here been saturated with either lime or 
silica. What we see is the carbon stain which was left 
when the cellulose particles of the wood were replaced 
by particles of lime or silica. 

Petrifacts on a smaller scale are often found in the 
so-called coal balls. These are hard, dark lumps which 
appear in coal seams, sticking out like raisins in a cake. 
They are masses of original vegetation preserved in their 
original form by saturation with lime or silica. The 
vegetation around them has been compressed and changed 
in form, but the lime or silica has preserved a certain 
area from compression or decay. 

Concretions called roof-nodules are found in shale 
formations above the coal seams. They sometimes 
contain well-preserved pieces of stems or seeds, but more 
often merely impressions of leaves. They are composed 
of plant materials deposited in the mud which covered 
up the coal swamps. If the plant forms were soon satur- 


20 



DELVING INTO A PREHISTORIC RECORD 


ated with ground water containing lime or silica, their 
whole structure was preserved. In most cases, however, 
the nodules were formed by a crystallization around the 
plant material which was too slow to preserve the whole 
structure, and merely retained an impression of the leaf 
or similar plant form. 

The plants and insects found embedded in amber are 
also petrifacts, because their whole organism is preserved 
perfectly. Even the color, which is lost in other petri¬ 
facts, remains unchanged. The plant or insect is mummi¬ 
fied, rather than turned into mineral. Such a fossil is 
valuable, because it is extremely rare. 

In fossils that are casts, or impressions of plants, merely 
the external form has been retained. The impression is 
frequently colored black by the carbon film which is the 
only remnant of the organism itself. In a cast, the stem, 
seed, or root, as the case may be, has been covered by 
mud or sand and a mold formed around the plant rem¬ 
nant. The organic matter has decayed inside the mold 
and left a hollow. This in turn became filled with mud 
or sand, which hardened into shale or sandstone. As a 
result, a positive cast was formed inside a negative one, 
in the exact external form of the stem, seed, or root. 

In the case of leaves and flowers, and sometimes of 
seeds, spores, roots, and stems, we get but an impression, 


21 



FERNS, FOSSILS AND FUEL 


not a cast. The organic matter has been compressed 
between the rocks in much the same manner as when we 
press a blossom between sheets of blotting paper or the 
pages of the family Bible. The external form is simply 
indicated by the stain of compressed carbon which is 
all that remains of the plant fragment. 

As a rule, we have impressions of the organs of trees 
and shrubs, but not of those of grasses and flowers. The 
leaves, seeds, and broken-off stems of trees and shrubs 
are carried into the water where they have a chance to be 
embedded in the mud and thus preserved. The grasses, 
flowers and other herbaceous plants usually decay on the 
spot and do not have organs that may easily be broken 
off and carried away. The toughest leaves and the 
woodiest fruits and seeds are the most easily preserved, 
because they can be carried some distance in the water 
without being destroyed. The soft and fragile tissues 
of grasses and flowers can be preserved only if they are 
embedded almost on the spot where they grew. 

To the paleobotanist, fossil hunting takes on all the 
aspects of a sport, although it is always a strenuous and 
sometimes a dangerous pastime. He follows up out¬ 
crops of shale in ravines, on river banks, on mountain¬ 
sides, clinging precariously while he hammers at the 
shale until the layer, sometimes only a few inches thick, 


22 




Figure i. A coal ball from Southern Indiana, containing 
a fossil seed (Trigonocarpus). Natural size. 

Figure 2. A section of a small stem out of a coal ball, 
showing the woody fibres. Magnified 75 times. 



FERNS, FOSSILS AND FUEL 


where the plant impressions are embedded, is located. 
Such a layer was once a river bottom, or the surface of 
a mud-bank of a stream, upon which plant material had 
been washed. 

He visits coal mines and walks through the corridors 
and chambers, following the seam. The shale above is 
often plastered with plant impressions, or fossil remains 
may be observed in the coal itself, or the roots of plants 
can be seen in the fire-clay below the coal. He picks up 
pieces of fossilized wood in ravines into which they have 
rolled, sometimes from uplands a long distance away. 
He staggers home at the end of a day’s exploring, laden 
with rocks of all sizes and shapes. 

He also finds fossils in the drill cores brought up 
during the testing of deep layers of rock for coal or oil 
deposits. The diamond drill often goes down into the 
solid rock as deep as 4,000 feet, and cuts out a core 
which is brought to the surface. When the core, part 
of which is usually of shale, is split open, it frequently 
shows plant impressions. 

Plant fossils that have been so laboriously gathered in 
the field must be taken to the laboratory for thorough 
examination, classification, and interpretation. The paleo- 
botanist always carries away from the field many more 
specimens than he could possibly want to keep; for it is 


24 



DELVING INTO A PREHISTORIC RECORD 


usually impossible, in a hasty examination at the time, 
to decide which are valuable and which are not. Many 
details would be likely to escape attention and excellent 
material thus be lost. So the bulk of the material is 
brought home; some is carried in knapsacks, and some 
taken in automobiles from the mine or ravine to the 
laboratory for study. 

There the material is first organized roughly. Similar 
things are put together to await definite determination 
of their place in the plant kingdom. The impressions 
and casts are hammered and picked at until they show 
the best appearance. Then they are placed in trays for 
careful investigation. 

Fossil woods and coal balls require a more complicated 
treatment before they can be studied. They have to 
be sliced into thin sections for examination under the 
microscope. This cutting is done with a rotary saw whose 
edge is charged with coarse diamond powder. The 
technical name for this saw is a diamond saw. The 
diamond powder cuts the hardest rock as easily as one 
cuts a loaf of bread with a kitchen knife, only a little 
more slowly. Great care must be taken to cut the coal 
ball in the right direction. The first cut must necessarily 
be more or less of a guess, but after the structure of the 
ball becomes apparent, the cuts can be made exact. 


25 



FERNS, FOSSILS AND FUEL 


The sections are cut as thin as the hardness or brittle¬ 
ness of the material will permit. Then they are polished 
on one side and cemented on a piece of glass. The 
exposed side of each section is put on a grinding disk 
and ground with carborundum until it is so thin that 
it is transparent. Another piece of glass is usually 
cemented on top to protect it before it is examined under 
the microscope. The cement used for this purpose is 
Canada balsam or a similar resin. 

This method of preparing coal balls for examination 
of the plant remains in them is extremely laborious and 
naturally requires a long time. Recently a much quicker 
process has been devised, which is now widely used in 
laboratories. The surface of the thin section sliced from 
the coal ball is smoothed and polished, then exposed to 
diluted hydrochloric acid. The acid eats away a thin 
layer of the lime which saturates the petrefact, and the 
cell structure and woody fibers of the plants stick up like 
the fine hairs of velvet. In petrefacts saturated with 
silica, hydrofluoric acid is used instead of hydrochloric 
for this etching. 

After the acid has been rinsed off with water and the 
surface dried, a thin solution of cellulose is spread over 
it, which soon forms a fine, perfectly transparent film, 
in which all the delicate organic particles left sticking 


26 



DELVING INTO A PREHISTORIC RECORD 


out by the etching process are embedded. The film is 
then pulled off, and brings with it the organic remains 
of the plant structure just as they were in the petrefact 
itself. The film can be mounted on a glass plate and 
examined under the microscope, just as is the ground 
section, and with much less time and work. 

When all the material has been organized and classified 
as accurately as possible, it has to be labeled and recorded. 
Then it is ready for description and interpretation in a 
book. In these interpretations of his laboratory, the 
paleobotanist tries to reconstruct the entire plant and its 
life history from embryo or seed to the adult age. He 
seeks to fit these forms into the evolutionary system of 
plants as far as it is known, and into the floras of the 
periods in which they grew. 

It is a long road from the newly discovered fossils to 
the printed page, but every step of it has to be covered 
before the job is finished. The work is not complete until 
the printed monograph or book with its precious additions 
to the world’s knowledge of the plants of other ages lies 
on the library shelf, where it will be ready for use in the 
interpretation and classification of still other fossils. 


27 



TWO 


THE CLASSIFICATION OF FOSSIL PLANTS 

I F WE knew everything about the evolution of plants, 
we could easily map all the ramifications of the 
great branches springing from the evolutionary tree in 
the plant kingdom. We could trace the plants of the 
present day back to their common origin and establish 
their relationships with each other. We could definitely 
classify these relationships and arrange all the plants 
under the heading of stems, orders, families, genera, and 
species, as we have been able to do much more completely 
with the different forms in the animal kingdom. 

The actual state of affairs, however, is far from this 
ideal condition. It is true that we have classified nearly 
all the living plants, but we know only a comparatively 
few of the myriads that must have existed in the course 
of the hundreds of millions of years that plant life has 
been on earth. The world’s present flora contains some 
300,000 species. If we imagine them as the base of an 
inverted pyramid, and their origin as the point on which 


28 


THE CLASSIFICATION OF FOSSIL PLANTS 


it rests, there must have been several millions of species 
in the time between this point of origin and the base of 
the pyramid today. Of these millions we know about 
30,000, most of them imperfectly, and all of them only 
in the upper portion of the pyramid; that is, in com¬ 
paratively recent geological times. 

There is one circumstance, however, that proves very 
helpful to the paleobotanist. The present plant kingdom 
contains not only the latest and highest types of plant 
development, but also many primitive and poorly de¬ 
veloped types. By comparing these types among them¬ 
selves, we can gain some idea of plant evolution. The 
science based on this comparison of living species we 
call the comparative anatomy of plants, or, sometimes, 
comparative morphology. This study is of great value, 
but the only real chronological evidence of the develop¬ 
ment of plant life is found in the fossil plants. 

By combining all our information from both compara¬ 
tive anatomy and fossil plants, we are led to the con¬ 
clusion that the plant kingdom is composed, in its 
evolutionary history, of six great stems, most of which 
are still represented, at least partly, in living floras. 

These stems are usually arranged in a rising order of 
development, from the simplest plant-forms to the highest 
and most complex. The first great stem is that of the 


29 



FERNS, FOSSILS AND FUEL 


thallophytes. The name is derived from the Greek word 
thallos , meaning bed or layer, and phyton, meaning 
plant. The thallophytes are a group of plants which 
are composed merely of a layer of plant-substance without 
differentiated tissues and, especially, without woody fibers. 

This stem is divided into two subdivisions, each of 
which is composed of numerous families, genera, and 
species. One of these subdivisions is the algae, or water 
weeds; the other is the fungi, to which mushrooms, molds, 
bacteria, and numerous other groups belong, having a 
low form of development and containing no green plant- 
substance. The possession of this green leaf substance, 
called chlorophyll, is the main distinction between the 
algae and the fungi. 

Under the microscope, chlorophyll grains appear as 
bands, spherical bodies, or variously shaped, saturated 
with a green substance which is the chlorophyll and 
which we can extract with alcohol or benzine. This 
substance makes possible the fundamental chemical 
process of organic life, consisting of the building up of 
organic from inorganic material. The carbon dioxide 
of the air and water is changed, under the influence of 
sunlight, into alcohols, starches, sugars, cellulose, protein, 
albumen, and a host of other chemical substances that 
are the bearers of life. This change takes place only in 


30 



THE CLASSIFICATION OF FOSSIL PLANTS 


chlorophyll-containing cells, and the sunlight is the energy 
which keeps the process in motion. The fungi, which 
have no chlorophyll of their own, are dependent upon 
the organic substances produced by chlorophyll-contain¬ 
ing plants, as is the entire animal world, including man. 

The opposite of this synthetic process, the building up 
of higher carbon compounds, or carbohydrates, from 
carbon dioxide and water, is the oxidation of organic 
substances back into carbon dioxide and water vapor. 
This is the process carried on through breathing, by 
which the energy needed for plant and animal life is 
produced. The complete chemical cycle is, therefore, the 
building up of organic substances from water and carbon 
dioxide through the energy of sunlight; using a part of 
this substance to form plant and later animal tissue, and 
decomposing the remainder by oxidation to supply the 
energy that keeps the life-cycle in motion. 

This oxidation is a slow process of combustion; it is 
exactly the same in its chemical nature, as the fast and 
intensive combustion which takes place when wood or 
coal is burned, releasing light and heat and producing 
carbon dioxide, water vapor, and ashes. The ashes are 
mineral substance which plant organisms always contain. 

When one eats an apple, for instance, the carbohydrates 
of the fruit, which had been produced from carbon 


31 



FERNS, FOSSILS AND FUEL 


dioxide and water by the plant itself, are assimilated by 
one’s digestive organs. The carbohydrates are partly 
used to build new tissues in the body and partly burned 
to supply the energy necessary to life. In the same way, 
when coal is burned to develop steam for industrial pur¬ 
poses or merely heat for cooking, there is used some of 
the energy that had been stored up by plants hundreds 
of millions of years ago in the form of carbon compounds, 
and fixed carbon made from carbon dioxide and water. 
If some of this energy is now released as heat and light, 
the carbon dioxide and water vapor at last return to the 
atmosphere, from which they originally came. This is 
the life-cycle which has been in operation on the earth 
for untold millennia. 

It is clear, therefore, that no organic life is possible 
without the synthetic process carried on by the chloro¬ 
phyll in plants. Green plants everywhere are the basis 
of other forms of organic life. Animals of all kinds 
are ultimately dependent on them; either they eat the 
organic substances which are produced by green plants, 
or they eat other animals which in turn have lived on 
plants. 

The fungi, which do not contain chlorophyll, are 
necessarily parasitic on other plants or on animals. They 
are a class of parasites which thrive on living organisms 


32 



THE CLASSIFICATION OF FOSSIL PLANTS 


or on dead plant or animal substances. To them belong 
the lowest known plant organisms like the bacteria and 
the amoebae, as well as higher types like the mushrooms, 
which grow in damp, moist places on decaying wood and 
leaves. Neither fungi nor algae have tissue; they are 
merely threads or flat plates of cells; even the most com¬ 
plex mushroom is a felt-like structure of cell-threads 
without real tissue. 

Among the algae, there are some enormous forms like 
the kelps and the tangs of the ocean, which grow to 
great length and float on the surface of the water. They 
are, none the less, primitive in structure and could never 
support their own weight in the air. Algae live in the 
ocean along the shelves of the continents or in stagnant 
bodies of fresh water. 

Another well-known member of the thallophytes is the 
lichen. They are an association of fungi and algae in 
which two kinds of plants live together, to their mutual 
advantage, in the relationship known as symbiosis. The 
algae produce the chlorophyll, and the fungi give support 
to the algae, getting nourishment from them. 

The next great stem is that of the moss plants or 
bryophytes. They are a slightly higher type of plant- 
life, and are accustomed to live on land. They are divided 
into the large groups of Hepaticae or liverworts, and 


33 



FERNS, FOSSILS AND FUEL 


Musci or true mosses. Among the true mosses we find 
a development of stems and leaves on a primitive scale. 
Their tiny stems, however, do not have a system of 
woody fibers. They are formed merely of longitudinally 
stretched cells. The leaves of the mosses have the shape 
of higher plant leaves, but consist of single layers of cells. 

All the mosses have a distinct alternation of sexual 
and asexual reproduction. The algae may reproduce 
non-sexually by spores only which germinate and grow 
into a new plant, or they may have an alternation of 
sexual and non-sexual reproduction as in the mosses. In 
the bryophytes the spores, which we can see in tiny cap¬ 
sules on mosses, germinate into small threads of cells 
from which the adult moss plant develops. The adult 
plant has small female egg cells, and male sex cells con¬ 
taining spermatazoa, which move to the egg cells and 
fertilize them. Out of the fertilized egg cell grows a 
capsule-like organ which contains spores, but which re¬ 
mains connected with the plant having the sex organs. 

The third great stem is that of the pteridophytes, or 
ferns and fern allies. They are the most highly developed 
of all the spore-bearing plants and include such types 
as the horse-tails (equisetales), club mosses (lycopo- 
diales), and true ferns (filicales). They, too, have an 
alternation of sexual and asexual reproduction. A spore 


34 



THE CLASSIFICATION OF FOSSIL PLANTS 


which falls out of the spore capsule on the reverse side 
of the fern leaf, will germinate on moist soil and form 
an almost microscopically tiny plant, which contains fe¬ 
male sex organs, with egg cells in them, and male sex 
organs containing spermatozoa. The spermatozoon works 
its way to the egg and fertilizes it, and out of the fertilized 
egg cell develops ultimately a full-grown spore-bearing 
plant. The large ferns and fern-like plants that we see 
in the woods represent only the asexual, or spore-bearing, 
generation of the plant. 

The lower plants share with the animals, including 
man, the possession of these spermatozoa, which are mi¬ 
croscopically small bodies having motion of their own 
by means of fine appendices by which they propel them¬ 
selves until they reach the egg cells, which they penetrate. 
The spermatozoon combines with the nucleus of the egg 
cell to form an embryo, which gradually grows into a 
fully-developed organism. 

There is, as we know, a great waste of material in 
Nature. Millions of spermatozoa are sent out, but only 
a very few egg cells are fertilized. The substance of the 
spermatozoon is one of the most marvelous mechanisms 
known, for, although it is almost inconceivably small, it 
contains within it the potentiality for producing all the 
characteristics of the adult form. 


35 



FERNS, FOSSILS AND FUEL 


Among the pteridophytes are several groups which 
have completely disappeared, such as the psilophytales, 
which are known only in a long-past geologic period, and 
the sphenophyllales which also became extinct at a very 
early date. Other members of the group are the horse¬ 
tails (equisetales), which date almost from the dawn 
of known plant life on earth; the club mosses (lycopo- 
diales), which date back to a very early period; and the 
true fern group (filicales), which are also extremely old. 
The ferns are the only group which seem still to flourish, 
for the horse-tail and the club moss are represented to¬ 
day only by insignificant types which cannot compare 
with the gigantic representatives of their orders that 
grew in early geologic periods. 

The groups of plants so far discussed are all called 
cryptogams or non-flowering plants because of their 
method of reproduction which is carried on by a single 
cell or spore. The next great group is that of the sper- 
matophytes or seed plants. They reproduce sexually 
by developing a seed which is not a single cell, but a 
complex, well protected body. 

Between the cryptogams and the spermatophytes there 
existed at an early geologic age a now extinct group called 
pteridosperms. These were a combination of seed plant 
and fern. They must have looked something like the 


36 




Branch of a Ging\o, showing fan-shaped leaves. From 
Missouri Botanical Garden, St. Louis. One-tenth natural 


size. 







FERNS, FOSSILS AND FUEL 


great tree-fern of New Zealand, or some large tree-wind¬ 
ing tropical fern, but they bore seeds of all sizes, by which 
they reproduced themselves. 

The spermatophytes proper are divided into two 
groups: the gymnosperms, which have free seeds either 
entirely uncovered or merely attached to the scales of 
cones, and the angiosperms, the seeds of which are always 
in capsules. Gymnos in Greek means naked, and angios 
covered; so their names describe them as naked-seed 
plants and covered-seed plants. 

The gymnosperms are divided into a number of orders 
which are in turn subdivided into families, genera, and 
species. The most important of these groups is the 
cycads or sago palms. Related to the cycads is another 
group which played an important role in previous geologic 
times, called the bennettitales or Cycadeoideae. Another 
group is represented today by the gingko tree, a queer form 
related to the cone-bearing trees, but having a fan-shaped, 
rather stiff leaf. It is an ancient tree that has defied 
time and looks today almost as it did millions of years 
ago. It would probably have died out but for the Brah¬ 
mins and Buddhists of the East, who selected it for their 
temple arbors and by cultivation perpetuated its life. 
No longer growing wild, it flourishes in parks and botan¬ 
ical gardens where magnificent specimens are to be seen. 


38 



THE CLASSIFICATION OF FOSSIL PLANTS 


The gymnosperms are best known to us by the conifers, 
to which belong the pines, hemlocks, spruces, cedars, 
and the host of other evergreen trees which grow all 
over the world. 

A group which is probably related to the conifers, but 
which became extinct long ago, is the cordaitales. They 
had large shafts and tufts of needle-like leaves of enor¬ 
mous size. Some of the leaves or needles were more than 
a yard long and two inches wide. 

The most highly developed forms of plant life are 
the angiosperms. The great majority of the familiar 
plants of today belong to this group, including all the 
foliage-bearing trees, the wild flowers, grasses, palms, 
shrubs, and innumerable others. The angiosperms are 
also divided into two groups, the monocotyledons and the 
dicotyledons, according to whether the seedling begins 
with one leaf, as in the monocotyledons, or with two 
leaves as in the dicotyledons. Most monocotyledons have 
long narrow leaves with parallel venation, as in the 
grasses or lilies, while most dicotyledons have complicated 
leaves with a midrib from which secondary veins spread, 
as in nearly all trees and shrubs and many of the flower¬ 
ing plants. 

Such a classification of plants as this, we call a biologi¬ 
cal one; it takes into account only their relations to each 


39 



FERNS, FOSSILS AND FUEL 


other and to the plants of the present era. We can also 
make a purely chronological grouping of the individual 
floras which have covered the earth successively during 
the great epochs of the past. This sort of classification 
we call geologic or stratigraphic. 

Concerning the oldest age of the geological series, which 
is usually called the Archeozoic, we have only theories, 
but we are bound to conclude that life in its lowest forms 
must have existed even then. The limestone and silica 
deposits of that time must have originated from organic 
secretions, and there are also graphite deposits whose 
carbon was undoubtedly derived from organic remains 
of some sort. There are large sedimentary accumulations 
dating from this early epoch. The formations which can 
now be traced back to that era constitute the complex of 
Archaean rocks, whose age has been estimated at 
1,300,000,000 years. We also know that there was much 
mountain raising during Archeozoic times and that at 
their close the North American continent was uplifted. 

The next great era we call the Proterozoic. Great sedi¬ 
mentary deposits of conglomerate sandstones, shales, and 
limestones, containing a large quantity of iron, have come 
down from it. We find formations of this age around 
Lake Superior, in the Rocky Mountains, in Canada, in 
Brazil, in China, and in South Australia. There are no 


40 



THE CLASSIFICATION OF FOSSIL PLANTS 


plant fossils from this age, except for some doubtful re¬ 
mains of algae, but there are sponges, corals, and worm 
trails. 

The Archeozoic and the Proterozoic may be considered 
merely the introductory chapters of the earth’s history. 
They correspond to the prehistoric era in the life of man 
on earth. The history of organic life for which we have 
ample documentary evidence in fossils is divided into 
periods corresponding to antiquity, the Middle Ages, and 
modern times. We have the Paleozoic, or Old Age of 
animal life, the Mesozoic, or Middle Age of animal life, 
and the Cenozoic, or New Age of animal life. These sub¬ 
divisions are based primarily on the main stages of animal 
development, rather than upon those of plant develop¬ 
ment. The development of plant life is always a step 
ahead of the animal devlopment; for, as we have pointed 
out, plants are the basis of animal life, inasmuch as they 
provide the food which makes any other form of life 
possible. 

The Paleozoic era may be roughly divided into an 
earlier and a later period. The earlier Paleozoic contains 
three subdivisions: the Cambrian, the Ordovician, and 
the Silurian periods. There are algal remains from all 
three periods and also many fossils of sea animals; fish 
were the most prominent form of animal life all through 


41 



FERNS, FOSSILS AND FUEL 


the period. Though we know nothing of the terrestrial or 
land flora, whatever it may have been, it was undoubtedly 
present, because plants appear in a high stage of develop¬ 
ment in the Devonian period with which the younger 
Paleozoic opens. 

Geologists divide the younger Paleozoic age into the 
Devonian, the Mississippian, the Pennsylvanian, and the 
Permian periods. From all of them we have large deposits 
of fresh-water sediments; in consequence we are acquainted 
with fossil remains of many land plants that flourished 
throughout this epoch. 

During the Pennsylvanian period, plant life reached a 
climax which resulted in the deposition of the material 
represented today by the bituminous and anthracite coal 
beds which form a circle around the northern hemisphere, 
in the United States, England, northern France, Belgium, 
Germany, Russia, Siberia, and China. 

At the end of the Pennsylvanian age and throughout 
the Permian, there was a great deal of mountain raising 
and a resultant cooling of the climate. Whenever the 
earth’s crust was disturbed to any great extent, there was 
an inevitable interruption of the usual warm temperatures 
and a temporary cooling. In some cases, as in the Per¬ 
mian period, this took place mostly in the southern hem¬ 
isphere, in contrast to the ice age which immediately pre- 


42 



THE CLASSIFICATION OF FOSSIL PLANTS 


ceded the present era, and which was concentrated in 
the northern hemisphere. 

During the later Paleozoic age, not only did land 
floras come into their own, but land animals made their 
first appearance. While we have well-preserved fossils 
of land plants from the lower Devonian, and must assume 
that they existed in considerable numbers during Silurian 
and probably Ordovician times, land animals seem to 
have first appeared in Pennsylvanian times and do not 
get fair sized until the Permian period. The plants had 
to be rather highly developed before land animals could 
exist. 

First the amphibians predominated, and later the rep¬ 
tiles. The reptiles come into their own in the Mesozoic 
era. This great epoch is subdivided into the Triassic, 
the Jurassic, and the Cretaceous periods. It was the day 
of the dinosaurs, gigantic reptiles which populated the 
land, the air, and the waters of the earth. Fishes, too, 
continued to flourish. 

Plant life in Mesozoic times is primarily represented 
by large cycads and other gymnosperms, while the Paleo¬ 
zoic was the era of the giant ferns (pteridophytes) and 
seed ferns (pteridosperms). During the Jurassic period 
the first birds appear. In the middle of the Cretaceous 
period, a sudden change in floras occurs. Flowering 


43 



FERNS, FOSSILS AND FUEL 


plants of the angiosperm variety spread like wild-fire, 
forcing the cycads into the background, where they have 
remained until our own day. The angiosperms have con¬ 
tinued to be the dominant flora of the earth. 

Toward the middle of the Mesozoic era a new type of 
animal began to appear. These were the mammals, 
destined to be the outstanding type in the next great era, 
the Cenozoic. 

The Cenozoic era is divided into the Tertiary period, 
during which it was still warm, and the earth was covered 
with rich tropical and sub-tropical vegetation from pole 
to pole, and the Quaternary, including the Pleistocene or 
glacial age, during which it was extremely cold in the 
northern hemisphere. 

The Tertiary period shows another climax, this one 
of animal development. Gigantic mammals like the hairy 
elephant, the hippopotamus, the rhinoceros, and the giant 
sloth now gave life and character to the landscape. The 
reptiles degenerated, and the animals of our own day 
began to develop. The horse was rising from a four¬ 
toed animal no bigger than a dog to the large, single-toed 
animal we know today. The earth was covered from 
pole to pole with forests of palms, laurels, cinnamon trees 
and similar tropical and subtropical plants. 

Toward the end of the Tertiary period great mountain 


44 



THE CLASSIFICATION OF FOSSIL PLANTS 


ranges rose, among them the Alps, the Himalayas, the 
Pyrenees, the Rockies, the Apennines, and the Andes. 
The climate gradually became progressively colder and 
immense ice-caps formed on the northern parts of the 
continents of North America, Europe, and Asia. They 
advanced and retreated several times, with alternating 
warming and cooling of the atmosphere, until the modern 
era in which we are now living dawned. Man, it is be¬ 
lieved, first appeared at some time in the Tertiary period. 

It is not known whether we are living today in a post¬ 
glacial or in an inter-glacial period. We may have passed 
out of the ice age entirely, as some geologists think, and 
in the course of another 100,000 years the climate may 
become universally warm again. Or, the glaciers and ice- 
sheets may come back again in the northern hemisphere; 
and the land where our present centers of civilization now 
stand, may in 10,000 years be covered with masses of ice 
hundreds of feet thick. 

Plant life depends on a number of what we call ecologi¬ 
cal or environmental factors. Ecology is a word closely 
related to economics. Just as human life is dependent 
largely on economic factors, which consist of food sup¬ 
plies, shelter, clothing, and many other necessaries which 
even a primitive man must have; so animals are dependent 
on food, climate, and habitat, such as water, forest, 


45 



FERNS, FOSSILS AND FUEL 


meadow, swamp, or desert. In the same way, plants, like 
all other living organisms, must have certain things that 
make their life possible. The most important of these are 
water, sunlight, temperature of the air, nutritious soils, 
and frequently an object to which to cling or which will 
furnish protection against excessive sunlight. These are 
some of the ecological factors of plant life, and the science 
which deals with them we call plant ecology. 

During the unfolding of geologic time, the most im¬ 
portant changes for plant life were in climatic conditions, 
involving primarily temperature and humidity. Every 
plant species requires a minimum temperature and a mini¬ 
mum amount of moisture for its existence, and cannot 
live beyond a maximum temperature and maximum mois¬ 
ture. These margins of safety vary with nearly every 
species. We find, therefore, different groups or associa¬ 
tions of plants in a tropical jungle, in an Alpine valley, 
in a desert, or in a swamp. The floras of the earth dur¬ 
ing geologic times reflect the changes of climate during 
those periods. 

The climate of the earth in past ages was normally warm 
and rather uniform, and periods of glaciation or extreme 
cold were very much the exception. The amount of mois¬ 
ture must have varied greatly, but the warm climate was 
usually accompanied by a sufficient rainfall, and a great 


46 



THE CLASSIFICATION OF FOSSIL PLANTS 


amount of dryness or aridity over large areas of the 
globe was exceptional. Besides the striking revolutions 
in climate, such as the Permian glaciation in the southern 
hemisphere and the Pleistocene glaciation in the northern 
hemisphere, there were a number of minor vacillations in 
climatic conditions; each one greatly influencing the exist¬ 
ing floras. 

If the climate gradually gets colder or drier, the animal 
life may adjust itself by migration or adaptation. Some 
animals move south or north, or uphill or downhill. 
They cover themselves with heavy hair or lose it. A 
plant’s only resource is adaptation by certain protective 
measures, for which there is but a limited opportunity. 
Those plant types which can not adjust themselves, die 
in the unfavorable regions, though they may continue to 
exist in more favorable portions of the globe. When con¬ 
ditions change again and become favorable once more 
in a given locality, such plants frequently move back, if 
no insuperable geographic barrier exists. This migration 
of plants, however, is slow. It depends upon the scattering 
of seeds by wind, water, and animals; it usually takes a 
great many years for a migrating plant to cover any 
considerable distance. 

This is what happened in Europe and North America 
after the glacial epoch. Plant life in the Tertiary period 


47 



FERNS, FOSSILS AND FUEL 


was much the same on both continents. The great ice 
shields which covered large portions of them both during 
the glacial period killed a considerable number of plant 
types, leaving only the hardy alpine or arctic species, 
which could exist near glaciers and ice fields. After the 
ice sheets disappeared, the remnant of the southern types 
could return. But in Europe they encountered an insuper¬ 
able barrier to their migration northward in the Mediter¬ 
ranean and Black Seas, and in the mountain chains 
which in Europe run mostly east and west; all of which 
were a result of glacial action. In North America, on 
the other hand, the mountain ranges run in a north-south 
direction, and there are no sea barriers; so the plants’ 
return to the north was unobstructed. Consequently, we 
now have distinctly different floras in northern Europe 
and North America, respectively. 

In the conclusions we draw from plants concerning the 
climate of geologic times we assume that the biological 
reactions of plants were the same then as in the present 
age. We apply the information derived from living 
plants to those of the past. Our entire knowledge of 
the structural and external conditions of fossil plants 
justifies this assumption. Fossil plants, indeed, have fre¬ 
quently been called the thermometer of geologic times. 

Besides the plant evidence, we also have other, but less 


48 



THE CLASSIFICATION OF FOSSIL PLANTS 


frequent, indications of climatic conditions during past 
ages. There is the mechanical work of glaciers, such as 
the piling up of moraines and the scratching of rocks. 
Soils are often preserved and show us whether the climate 
was dry or moist. In some instances we can reconstruct a 
topographical map of a geologic landscape, showing the 
distribution of mountains, rivers, lakes, and swamps. We 
can with great accuracy determine the seashore of various 
geologic horizons by the deposits of limestone and of 
shells of marine animals. All such indications taken to¬ 
gether present conclusive evidence of the climate of a 
region during any geologic period. 


49 




THREE 

THE BEGINNINGS OF PLANT LIFE ON 
EARTH 

A PPARENTLY life in some form appeared on the 
JL JL earth as soon as the conditions of temperature were 
favorable. We really know nothing about the origin of 
life; everything that is said on the subject is speculation, 
based on what is known about life’s development. But 
the human mind has an irresistible desire, which philoso¬ 
phers have called the metaphysical urge, to fill in the gaps 
in our scientific information with theories which will ex¬ 
plain, in a reasonable way, that which is wrapped in dark¬ 
ness. It is constantly attempting to form workable hypo¬ 
theses about important events which we have not been 
in a position to observe, and about which we cannot col¬ 
lect dependable knowledge. 

It is not to geology, however, that we must turn for an 
explanation of the origin of life, but to bio-chemistry. 
The latter teaches us that life functions have their begin¬ 
ning in the colloidal stage, which is a condition not 
strictly liquid or strictly solid but that of a jelly which 


SO 




THE BEGINNINGS OF PLANT LIFE 


is rather unstable, both physically and chemically. Ex¬ 
tremely simple and very small organic bodies may form 
themselves from inorgmic colloids under the influence of 
sunlight, and from these in turn, reacting upon one an¬ 
other, may develop more and more complex organic com¬ 
pounds. As this complexity increases, the bodies acquire 
the ability to utilize light-energy for further develop¬ 
ment of structure. In this manner, the gulf between non¬ 
living and living things must have been bridged and a 
spontaneous emergence of life occurred. At just what 
point these structures ceased to be mere organic com¬ 
pounds and became living organisms we cannot be sure; 
but we are convinced that these first living organisms did 
not stand even at the level of bacteria, but at a level of 
life far below anything the microscope can reveal. 

The next stage in the evolution of life is probably to 
be found in those bacteria which can grow on inorganic 
substance and synthesize proteins and carbohydrates from 
carbon dioxide, inorganic nitrogen, and sulphurous and 
phosphorus compounds. The step from such synthesizing 
bacteria to algae which contain chlorophyll probably fol¬ 
lowed next, and with the coming of the chlorophyll to 
utilize the sun’s energy, life on a large scale became pos¬ 
sible for the plant kingdom. 

The places where life sprang up and gradually formed 


51 



FERNS, FOSSILS AND FUEL 


itself from sub-microscopic organisms through bacteria 
to algae were the seashores and perhaps the deltas of rivers 
and the edges of swamps and creeks. It is difficult to say 
whether salt or fresh water was first inhabited by living 
organisms. In any event, it was undoubtedly shallow 
waters that saw the origin of life, for there the conditions 
of light, temperature, and pressure would be more favor¬ 
able than at greater depths. Probably life originated in 
numerous places and gradually spread, filling all the 
coast lines, rivers, and swampy places, and from these 
crowding farther and farther into the highlands. 

In trying to visualize a picture of the vegetation of any 
given time during the Cambrian and Silurian periods 
of the earlier Paleozoic era, we should think of a coast¬ 
line whose waters are full of algae. There are green, 
brown, red, and blue water weeds; some mere floating 
ribbons, others twenty or thirty yards long and divided 
into many branches attached to rocks and floating in 
the clear warm water. This forest of water plants is 
inhabited by numerous sea-stars, sea-urchins, sea-ane¬ 
mones, jelly-fish, sponges, sea-lilies that had a plant-like 
appearance, but were animal bodies, sea-cucumbers, and 
corals of different colors, forming large reefs. Innu¬ 
merable shells are lying on the bottom of the sea, while 
others have been thrown up on the shore itself. Worms 


52 




Impressions of fossil ferns and fern allies from the Pennsyl¬ 
vanian. Natural size. Figure i: A fern leaf (Sphenop- 
teris). Figure 2: A fern leaf (Neuropteris). Figure 3: 
A fern leaf (Pecopteris). Figure 4 : A branch of a horse¬ 
tail (Calamites). 













FERNS, FOSSILS AND FUEL 


crawl on the bottom of the sea, and nautilus shells sail 
over the surface. Some fish are already present. 

The most characteristic animal of the Cambrian and 
other early Paleozoic periods, however, was the trilobite, 
a flat crustacean that varied greatly in shape; in size it 
was from a few inches in length to two feet. A crustacean 
is an animal form whose skeleton is purely external. The 
flesh is inside a sort of armor which protects the soft 
part of the body and keeps it together. The trilobite 
was covered with this sort of hard shell and consisted of 
a head and many joints, which became more and more 
elaborately constructed before it died out at the end 
of the earlier Paleozoic era. It had horns, as well as all 
kinds of appendages on its joints, and must have given 
a strange appearance to the Cambrian, Ordovician, and 
Silurian seas. 

The trilobites became extinct by the end of the Silurian 
period. Perhaps they had too many enemies among the 
rapidly multiplying fish; perhaps they were the victims 
of a tendency in nature to which every family, genus, and 
species is exposed. That is, every living form has a begin¬ 
ning in the history of life on earth, and a time when it 
flourishes. Then it declines and disappears. In some 
types, this cycle may take only a comparatively short 
time in the geological ages; in others, it may stretch over 


54 



THE BEGINNINGS OF PLANT LIFE 


a great many periods. In a few instances, a type seems 
practically to defy time and age. But the history of a 
human individual, with its birth, youth, adulthood, sen¬ 
ility, and death, seems to repeat itself with considerable 
regularity in types of plants and animals, as well as in 
royal dynasties and human races. 

Since deposits of sediment from early Paleozic times 
are all of marine origin, we can reconstruct the aquatic 
life from facts. They are much richer, however, with 
regard to animals than to plants. It is more difficult, 
and entirely hypothetical, to try to picture the land life. 
The first fossil land plants are found in Lower Devonian 
times, and the first land animals in the Pennsylvanian 
period; but there must have been a land life at least along 
the seashore at a much earlier date, because in these first 
remains the land plants and land animals are already con¬ 
siderably developed. By the time of the Upper Devonian 
period, we find extensive forests of big trees which must 
have had behind them a long history of development, 
exceeding by far the length of a single geologic period. 
Some day we may find traces of this development in 
the rocks. Meanwhile, we have to be content with a 
theory. 

Perhaps in the Cambrian, surely not later than the 
Ordovician period, an amphibious type of land plants 


55 



FERNS, FOSSILS AND FUEL 


must have developed along the water’s edge. These were 
plants which could live in water and could continue to 
exist in moist places where the sea had receded or the 
tide ebbed, in shore swamps that had been uncovered 
by the sea, or in the deltas of great rivers. Gradually 
life crept into the valleys, clinging first to moist and 
swampy places, and later reaching out to the uplands, 
until the narrow bands that had edged the water widened 
and covered the continents. 

How did these early land plants look? We can draw 
some conclusions from the oldest land plants we find in 
the Lower Devonian period. These plants already had 
attained a more or less advanced stage. They can be 
classified among the pteridophytes or fern types, although 
they are primitive and show many features of a moss 
or algalike character. 

The first land plants could only have originated from 
algae. They were probably composite types, which com¬ 
bined features of algae, mosses, and pteridophytes. We 
find that original types from which other types later de¬ 
velop nearly always combine the features of several groups. 
The types which develop from these primitive forms have 
specialized in one feature and have become rudimentary 
in all the other features. It is a progressive specialization 
which seems to have created new forms. 


56 



THE BEGINNINGS OF PLANT LIFE 


The algal types try to adjust themselves first to tem¬ 
porary and then to permanent land life. They seem to 
have tried a variety of adjustments. Some of them 
adopted one of these adjustments, discarded the others, 
and became mosses. Others became pteridophytes in the 
same process, and others may have become gymnosperms. 
It is not a case of mosses developing from algae and 
pteridophytes from mosses and so on up the scale of 
plant life. All developed simultaneously from a com¬ 
mon beginning, the algae. Already a number of sub¬ 
divisions of the pteridophytic group, for instance, had 
originated at an early date. In these subdivisions it 
may have happened that some algae specialized along 
the lines of ferns, others along the lines of club-mosses, 
while others became horsetails. Probably a great many 
different types originated almost simultaneously from 
a variety of algal types. There is always a multiplicity 
of origins, just as among the higher animals some rep¬ 
tiles became mammals, and others became birds. 

The same new type, genus, or species, may even have 
developed simultaneously in different places from different 
plants. A species or a genus or a family does not neces¬ 
sarily go back to one common origin; it may spring from 
several sources. It is well to keep in mind the fact that 
Nature is enormously resourceful, and that different 


57 



FERNS, FOSSILS AND FUEL 


causes may bring about the same result. The possibility 
that a variety of processes springing from diverse circum¬ 
stances may lead to the same result is often overlooked, 
when a phenomenon is explained by a single hypothesis. 

The green carpet which spread over the earth from the 
edges of the ocean and the deltas of rivers, and which first 
followed the water-courses and only later rose to the 
highlands, consisted probably of small moss-like plants, 
which were not actually mosses, but only looked like them. 
Among these, there were larger, grass-like plants, not 
true grasses, but resembling them in appearance. With 
the progress of time came larger plants looking much 
like ferns and club-mosses and horsetails of our day. 
Some of these types developed into shrubs, and some 
of the shrubs developed into trees. 

By the beginning of the Devonian period, all these 
forms, including great trees which, though unlike our 
present trees, constituted the prairies and forests of the 
time. The colors of this vegetation were probably green, 
brown, yellow, and black; no striking colors, such as red 
or blue, interrupted the comparative monotony of this 
primitive color scheme. The brighter colors probably 
came much later, and were useful in attracting insects to 
help in the reproductive process by carrying pollen dust 
from one plant to another. 


58 



THE BEGINNINGS OF PLANT LIFE 


Animal life among this very first land vegetation must 
have been either entirely absent or extremely primitive. 
There may have been worms, and perhaps some insects like 
the ancestors of the cockroaches. Some scorpions may 
have crawled along the ground. The poverty of the 
land fauna is in striking contrast to the teeming life of 
the ocean, which was full of fish, crustaceans, starfish, 
crawfish, mussels, oysters, jelly-fish, and corals. 

Away from this highly developed and multi-colored 
sea life, the land flora and fauna must have played the 
role of pioneers. Like the frontiersmen of early North 
American history, who left their comfortable homes along 
the Atlantic seaboard or in Europe to take up a life of 
untold hardship in some rude settlement in the Missis¬ 
sippi valley, these plants and animals ventured slowly 
from the coast-line into the valleys and uplands. There 
is a heroic spirit inherent to all organisms, from the most 
primitive animals and plants to man himself, which 
reaches out for new adventures and has an irresistible urge 
to expand into the unknown. This will to master the 
environment is a counterpart of the will, in man alone, 
to understand the unknown in the intellectual and spiritual 
realm. All our progress may be summed up in two 
urges: the physical urge to conquer Nature, and the 
metaphysical urge to comprehend the things of the spirit. 


59 



FOUR 


THE ERA OF THE FERNS 

E ARLIEST fossil land plants that have been dis¬ 
covered come from the early Devonian period. 
While rock impressions of plants of that age have been 
found in various parts of America and the Arctic, the 
only source of our knowledge of their structure is a 
large bed of petrifacts discovered in 1915 near the 
village of Rhynie in Aberdeenshire, Scotland. A swamp 
seems to have existed there near a seashore in early De¬ 
vonian days, and was exposed to inundations from time 
to time. It also happened that a geyser or some powerful 
mineral spring was located near the swamp and frequently 
soaked it with water containing a high percentage of 
silica. The result was that the plant life of the swamp 
was impregnated with silica, and thus consecutive layers 
of petrifacts were preserved. 

Nowhere else do we find any evidence of the anatomi¬ 
cal structure of early Devonian plants. Two Scotch 
paleobotanists, Kidston and Lang, examined this material 


60 


THE ERA OF THE FERNS 


and published the results in a series of articles in the 
Transactions of the Royal Society of Scotland . From 
the well-preserved petrifacts it was possible for them to 
reconstruct the form of the land plants in detail. They 
analyzed them and compared them with the more primi¬ 
tive plants of the present day. 

It is well, however, to keep in mind that these very 
primitive types of fossil plants, found in the old red sand¬ 
stone formation of early Devonian times, do not neces¬ 
sarily represent the highest type of plants which grew 
during that period. There must have been a great many 
other types; to draw final conclusions from this single 
locality and the single group of plants found there would 
be as foolish as it would be for one to try to establish 
a complete modern flora by merely examining a mossy 
swamp or a grassy meadow, in France or England, and 
nothing else. 

Kidston and Lang established that their plants were 
a composite type which contained features of the pterido- 
phytes, the mosses, and the algae. There were different 
genera and species. The simplest did not even have 
leaves, but the highest types bore a scaly type of leaf. All 
these plants seem to have been of a creeping moss-like 
character, with little vertical stems one to four inches high, 
bearing small spore-capsules at their ends. The stem 


61 



FERNS, FOSSILS AND FUEL 


was a tiny woody cylinder, reminding us of certain pterido- 
phytes, while the spore-capsules were similar to those of 
mosses. Early impressions of this kind of plant had 
been found in other Devonian localities and had been 
assigned to the genus Psilophyton, and the newly discov¬ 
ered structural material was therefore given the name 
psilophytales. One of the genera got the name Rhynia 
from the place where it was found. 

It seems that the psilophytales had sprung from highly 
organized algae, and that some important features of 
structural difference had already been acquired during 
their marine life. This high algal type left no traces. 

The exact place of the psilophytales in the biologic sys¬ 
tem of plants is uncertain. They do not show a dis¬ 
tinct affinity to any of the great subdivisions of living 
plants. Some botanists have emphasized their similarity 
to mosses, while others have laid great weight on features 
that are similar to the pteridophytes. Perhaps other strik¬ 
ing discoveries may some day be made which will widen 
our knowledge of early Devonian plant structure and 
will clear up the uncertainties. Until that happens, it 
will be impossible to make a complete picture of the early 
Devonian landscape, nor will it be feasible to assign a 
definite place in the biological system of plant life to 
the psilophytales. 


62 



THE ERA OF THE FERNS 


We may imagine that the shores of the early Devonian 
seas were covered with plants of the psilophytales type. 
But we are bound to conclude that more highly developed 
plants also existed at the same time, because in the later 
Devonian period we find stems of trees many feet long 
and more than two feet in diameter. These could not 
have sprung into existence overnight. 

In the State Museum at Albany, New York, there 
is a reconstruction of a later Devonian forest which is 
much more complete than anything we have from the 
earlier period. It is based on remnants and fossils found 
near Gilboa, New York, which have given us a fuller 
knowledge of the plant life of that period. The recon¬ 
struction is painted in the background, while actual rocks 
and petrified stems from Gilboa fill the foreground. The 
restored forest, which is based on most accurate studies 
of the fossils, shows trees more than thirty feet high, but 
otherwise little different from the ferns of our age. 

An interesting feature is the presence of seeds on some 
of these tree-ferns, which make them the connecting link 
between true fern plants and seed plants. The existence 
of such a connection, between two now widely separated 
types, in the early Paleozoic age has been emphasized 
in an earlier chapter, where this type was called pterido- 
sperms. They are thus known to be as old as the true 


63 



FERNS, FOSSILS AND FUEL 


fern plants and as the gymnosperms, which are true seed 
plants. Their common origin, if there was one, must 
have existed at a much earlier date, probably contempo¬ 
raneously with the psilophytales and possibly even earlier. 

It is to the credit of the Curator of Paleobotany in the 
New York State Museum at Albany, Miss Winifred 
Goldring, that the Gilboa flora has been worked out 
in such minute detail, and she has made us especially 
familiar with one type of a seed-bearing, fern-like tree 
to which she gave the name Eospermatopteris, meaning 
“early seed fern.” The resconstruction at Albany also 
shows that there were tree-like club-mosses of considerable 
size in the late Devonian period. These come to a high 
development in the next two periods, the Mississippian 
and the Pennsylvanian. 

A third large group of plants represented in restora¬ 
tion at Albany are tall gymnospermous trees, distantly 
related to our present-day conifers. Late Devonian floras 
of all these types are known from many other parts of 
the world, from Europe, Asia, North America, and the 
Arctic. 

In the Mississippian formation, which follows the 
Devonian, extensive marine deposits were laid down, but 
the fresh-water deposits are comparatively small. There 
are a great many plant fossils and still more fossil shells 


64 




Devonian landscape, reconstructed in the New Yor\ State Museum, Albany. 





























































FERNS, FOSSILS AND FUEL 


from Mississippian times in America, and from the Kulm, 
which corresponds in Europe to the Mississippian. The 
flora represents a more or less intermediary stage between 
that of the Devonian and that of the Pennsylvanian 
period which follows it. 

During Pennsylvanian times, vegetation flourished 
luxuriantly, and the great beds of bituminous and anthra¬ 
cite coal of North America were formed. The best coal 
seams of Europe and Asia also belong to this period. 

The name Pennsylvanian is given to the coal age in 
this country because the type formations, where the geol¬ 
ogy of the period was first studied on this continent, are 
in Pennsylvania. A type formation is a local deposit 
after which a geologic horizon is named, because the 
rocks that were formed during it were first studied in that 
particular place. The older Pennsylvanian in America 
corresponds in Europe to the Westphalian whose type 
formations were first studied near Westphalia in Ger¬ 
many. The younger Pennsylvanian in this country is 
the same as the Stephanian in Europe, whose type for¬ 
mation is near St. Etienne in France. 

In Russia, the formations of the great coal age were 
first studied in the deposits near Moscow and in the 
Ural Mountains. The following tabulation shows this 
correlation of the Pennsylvanian of North America 


66 



THE ERA OF THE FERNS 


with the formations of Eurasia: 


North America 

1. Upper 
Pennsylvanian 
(Monongahela) 
(Conemaugh) 


Western and 
Central Europe 

1. Stephanian 


Russian and 
Siberia 

1. Ouralian 


2. Middle 
Pennsylvanian 
(Allegheny) 

3. Lower 
Pennsylvanian 
(Pottsville) 


2. Westphalian 


2. Moscovian 


The greatest coal deposits of the world are found in 
the Pennsylvanian formation, but there is coal also in 
a number of other formations like the Mississippian in 
America and the Kulm in Europe, and in nearly every 
period after the Pennsylvanian. The coal fields of the 
southern hemisphere belong primarily to the period im¬ 
mediately following the Pennsylvanian, the Permian. 

Twice in the history of the earth an enormous accumu¬ 
lation of plant material has occurred, and it was then 
that the greatest coal beds were laid down. These two 
periods are the Pennsylvanian and the middle of the 
Tertiary. There must have been a coincidence of cli- 


67 




FERNS, FOSSILS AND FUEL 


matic conditions highly favorable to plant growth at 
both times; for otherwise it would be inconceivable that 
coal beds, which are nothing but accumulated carbonized 
plant material, could have been deposited to such a vast 
extent. 

There is another fact which we must not overlook. 
The coal beds of the Pennsylvanian period, as well as those 
of the Tertiary, extend from near the north pole down 
into the temperate zone, throughout North America, 
Europe, and Asia, including Alaska, Greenland, Spitz- 
bergen, Siberia, and many Arctic islands. Apparently 
the north pole must have been in about the same place 
in those times as it is now. This puts a very awkward 
question before us. We can explain a mild temperature 
from pole to pole, but it is impossible to explain by any 
stretch of the imagination how the polar night was 
illuminated to permit a constant plant growth. 

We know very well that plants cannot grow without 
light; yet the trees of the Pennsylvanian period do not 
even have annual rings indicating seasonal changes of 
growth. How could a tropical or semi-tropical vegeta¬ 
tion more abundant than that of our times have grown 
in the polar darkness? The only theory which can explain 
it is the assumption of continental movements. If the 
continents in Pennsylvanian times were arranged in a 


68 



THE ERA OF THE FERNS 


different way than they are now, the regions which are 
now Arctic could have been in much more southern 
latitudes, where luxuriant plant life was possible. While 
there are great difficulties in explaining the mechanism 
of continental movement, nevertheless it seems to be 
gaining ground steadily. 

During the Pennsylvanian period, great bays reached 
into the interior of North America from the Gulf of 
Mexico. These bays were frequently above the level of 
the sea and as often fell below it. In Illinois, for instance, 
they rose above the sea level at least sixteen times and 
were sixteen times covered by inundations. Similar bays 
extended throughout Pennsylvania, West Virginia, Ohio, 
eastern Kentucky, Tennessee, and Alabama. Another 
bay stretched through Texas, Arkansas, Oklahoma, Mis¬ 
souri, and Iowa. One of these bays filled practically all 
of Illinois, western Indiana, and western Kentucky. How 
the various bays of North America were connected with 
each other and with the Gulf of Mexico is not yet quite 
clear. A bay also extended into northern Michigan but 
probably was early detached from the rest. 

When these great inland bays rose above the surface 
of the sea, or, in other words, when the sea level receded 
a few feet, opportunity was given for the development 
of extensive shore swamps. When the sea advanced again, 


69 



FERNS, FOSSILS AND FUEL 


these swamps were destroyed by water and by sand and 
mud. This process repeated itself many times, and each 
time accumulated vegetation was covered up and buried 
in thick mud and sand. This compressed and buried 
swamp vegetation turned into coal seams. 

There are as many coal seams in Illinois as there 
were subsidences of these bays to a point below water 
level. Each inundation of the swamp left shale, sand¬ 
stone, or limestone beds above the coal. The plants of 
the swamp left their leaves, stems, reproductive organs, 
and seeds in the shales and sandstones that covered the 
swamps, and their roots are frequently found in the old 
subsoil of the swamp which became the clay bed on which 
the coal seam rests. The result is that we have a large 
number of plants preserved from the Pennsylvanian 
period, but they are all remnants of swamp flora and do 
not represent the upland vegetation of that period. We 
know practically nothing about the latter except what 
we may infer from some of the fossil woods and seeds 
that we occasionally find in sandstones or which have 
been washed out of them and can be picked up in the 
ravines between the Pennsylvanian rocks. 

The shore swamps of the Pennsylvanian period were 
probably intersected by rivers, and the deltas of these 
old river beds are now the best fossil plant deposits. 


70 



THE ERA OF THE FERNS 


Near Morris and Wilmington in northern Illinois, such 
a river delta probably existed in early Pennsylvanian 
times. In that region we find several of the oldest known 
fossil plant localities of North America. The fossils can 
be dug out of the banks of the Mazon Creek and from 
the mines southwest of Wilmington; in fact, we can 
restore a Pennsylvanian landscape from the many 
thousands of plant impressions that are found there. 
Specimens have been collected for many years in this 
stretch of land, and probably almost all of the fossil 
plant species that ever were preserved in this locality have 
been identified. There is no other place in North 
America that has been more thoroughly explored for 
fossils. Nevertheless, it has not been possible to assemble 
more than one hundred plant species from Mazon Creek. 

There must have been a great monotony in that swamp 
forest. The predominant types were fern-like plants, 
many of them bearing seeds (pteridosperms), while some 
were true ferns. These fern-like types were either tree- 
ferns or climbing ferns. Some were shrubs, and others 
even herbaceous plants. There was a dainty little fern 
which later got the generic name Sphenopteris , which 
means wedge-shaped fern, because the leaves were cut 
up into small wedge-shaped sections. Another fern was 
the comb-fern (Pecopteris). There was the broad-leaved 


71 



FERNS, FOSSILS AND FUEL 


Neuropteris, and the Alethopteris, whose leaflets formed 
elegant little curves. Another, the Odontopteris, had 
tooth-shaped leaflets, while the Callipteridium, meaning 
the beautiful fern, had oblong leaflets with delicate ven¬ 
ation. There was a water plant called Sphenophyllum, 
which is now entirely extinct. Its branches drifted in 
the water and bore whorls of wedge-shaped leaves in 
multiples of three, usually having nine leaves to a whorl. 
At the ends of its stems were spikes with whorls of 
spore-capsules. 

The giants of the forests were the big club-moss plants 
(lycopods), which were trees sometimes one hundred 
feet high and with trunks three or four feet in diameter. 
The stems or trunks were forked and had tufts of grass¬ 
like leaves at the ends of the branches. They all bore 
large cones filled with innumerable spores. The bark 
of these great lycopods resembled an alligator’s skin. 
Some had rhomboid impressions arranged in spirals and 
this type was called Lepidodendron, which means scale- 
tree. Others had rows of hexagonal or round impressions 
which resembled the wax seals formerly used to close 
letters. This type was called Sigillaria. In addition to 
these, there was a great variety of other lycopod types. 
The ornamentation of the bark is used as the principal 
character for establishing subgenera and species. 


72 



THE ERA OF THE FERNS 


Between the great shafts of the lycopods of the Penn¬ 
sylvanian forest, another plant type was visible, the 
cordaitales. They were a plant somewhat related to the 
modern conifers, but they did not belong to exactly the 
same class. These large trees bore enormous needles, 
sometimes three feet long and from one-half to four 
inches wide. 

There was also an abundance of tree-like horsetails 
(equisetales), of which the principal genus is called 
Calamites, which is a generic name for the stem form of 
the plant. The leaf of the Calamites was found and 
identified after the stem had been described and put 
into several species of Annularia. Some of these leaves 
are very dainty and could well be used by artists for 
decorative purposes. 

There were no flowers of the kind we have now in 
the swamp forests, and the vegetation was monotonously 
green, brown, and yellow, unrelieved by the brighter 
colors of red, blue, and purple. A great silence pervaded 
the world of that time, for there were no birds singing 
in the trees; no butterflies, nor bees, nor flies humming 
through the air. The only sounds which broke the quiet 
were the croaking of small reptiles and the faint buzz 
of gigantic dragonflies whose wing-spreads often reached 
thirty inches across. They were the most conspicuous 


73 



FERNS, FOSSILS AND FUEL 


insect forms. Many cockroaches, however, climbed over 
the plants. There have been found over a thousand 
fossil cockroach species, more than half of which lived 
in the Pennsylvanian period. The waters were full of 
fish and little crustaceans, but the big trilobites had by 
this time disappeared. The oceans had a vigorous animal 
and plant life, but while the land floras had attained a 
high development, the land animals were still in an 
early stage and far behind their marine contemporaries. 

The swamps were filled not only with living plants 
but with an enormous quantity of dead plant matter. 
Dead stems, leaves, spores, and seeds were often piled 
many feet high. 

The low mountains may also have been covered with 
forests of lycopods and tree-ferns, though few traces of 
this vegetation have survived. The sky was probably 
cloudy most of the time, and the air full of moisture 
and warm all the year round. There was no change 
of seasons, no fall and winter, only an eternal spring 
and summer. If a person could be transplanted into 
one of these Pennsylvanian swamp forests, he would not 
feel a greater change than if he went from the temperate 
zone to a jungle along the Amazon river. In spite of 
the absence of flowers, the general type of plant life 
was not greatly different from our own. The species 


74 



THE ERA OF THE FERNS 


were different, but the biological functions were much 
the same. Plants lived, grew, and reproduced them¬ 
selves in the same way they do now. 

An enormous time must have elapsed in the evolution 
of plant life on earth from its earliest stages to the very 
high level it had reached in the Pennsylvanian—a level 
which is very close to that of today. Yet the Penn¬ 
sylvanian period belongs to the Paleozoic, or Old Age, 
in the known history of organic life. The unknown 
history must have been infinitely longer. It must have 
extended into many hundreds of millions of years. The 
Pennsylvanian floras existed at least 300,000,000 years 
before our time, and yet they belong to our time. Plant 
evolution must be imagined as an endless procession of 
species of which we can see only the foremost groups. 

The Permian period, which follows the Pennsylvanian, 
shows a glacial epoch in the southern hemisphere, and 
the deposition of red beds, which indicate dryness. A 
sweeping climatic change seems to have come about in 
a comparatively short time. In consequence, a reduction 
of the vegetation occurred. 

While the type locality of the Permian period is in 
northeastern Russia, its best development occurs in the 
southern hemisphere, where the great glaciation of the 
era took place. Permian life is nowhere better developed 


75 



FERNS, FOSSILS AND FUEL 


than in the great Karoo formation of South Africa. 
It is also found in large deposits in Texas and in some 
other parts of North America, and it is prominent in 
Australia and in India. 

The plant life in the Karoo deposits showed plainly 
the influence of the ice cap which radiated from the South 
Pole during the period. The vegetation was considerably 
less than that of the Pennsylvanian period. A new 
fern-like plant became dominant in the southern hemis¬ 
phere, called the Glossopteris , or tongued fern, because 
its leaves were tongue-shaped. It was a rather small 
plant, with leaves attached to creeping stems. These 
stems looked like the human spine and were therefore 
called Vertebraria. The Glossopteris must have filled 
the plains and valleys like a weed or grass, for its leaf 
impressions are found everywhere throughout the Permian 
period in the southern hemisphere. It never penetrated 
to southern Europe or North America, but from India 
it entered the continent which at that time filled the 
place of the modern Ural Mountains and in this way 
penetrated far into the northern hemisphere. It was 
probably a seed fern, not a true fern. 

Some other fern-like genera of the Pennsylvanian 
period survive in the Permian Karoo, among them the 
Pecopteris and the Callipteridium. A new element 


76 



THE ERA OF THE FERNS 


appears, however, in the form of various conifers which 
are heralds of the domination exercised by the gymno- 
sperms in the following periods of the Mesozoic age. The 
great lepidodendrons and sigillarias of the Pennsylvanian 
period are disappearing and so are most of the seed 
ferns (pteridosperms). The giant equisetales become 
extinct and the sphenophyllum also disappears. Smaller 
types of lycopods and equisetales continue, and the seed 
ferns apparently have already given issue to a new type 
which spreads rapidly, the cycads. 

The desert-like landscape of the Karoo, with its not 
over-abundant vegetation, was populated with fair-sized 
reptiles of the great tribe which was to produce the 
giants of the Mesozoic age. They already show a 
tendency toward the grotesque appearance that is so 
pronounced in the next age. One of these Permian 
reptiles, called the dimetrodon, was about eight feet long 
and had spines about four feet long attached to its 
vertebrae and connected by a membrane which formed a 
fan-shaped screen on its back. Other reptiles of the 
period were lizards four feet long, like varanops, and 
giant salamanders. In the northern hemisphere, in 
Texas, where there was no glaciation and where we find 
a more opulent vegetation, though of the same type, 
great water reptiles also lived. 


77 



FERNS, FOSSILS AND FUEL 


It was supposed originally that the entire Karoo beds 
had been deposited by the great lakes and rivers draining 
the southern glacial ice caps, but recently others have 
compared them with the wind-borne deposits (loess) of 
the northern glacial epoch. The Karoo was undoubtedly 
a region in which the dust of the desert had been accumu¬ 
lated in large quantities by wind drifts. Similar sand 
deposits are formed nowadays in the deserts of South 
Africa, although the climate is warmer now than it was 
in the Permian period, because of the retreat of the 
extensive ice fields that existed then around the south pole. 


78 



FIVE 


THE ADVENT OF FLOWERING PLANTS 

D URING the Permian period, a noticeable change 
in the plant life had taken place. The vegetation, 
which before this time had been composed predominantly 
of seed ferns (pteridosperms), club-moss trees, and a few 
gymnosperms, became more and more gymnospermic, 
until by the end of the period it was overwhelmingly so. 
The conifers appeared, the cycads flourished, and the 
predominance of the gymnosperm types of plants began. 
They came to their highest development in the Triassic 
period which follows the Permian, and they held first 
rank through most of the Mesozoic age. 

The famous petrified forest near Andamana, Arizona, 
is a typical Triassic landscape. In it, the most conspicuous 
trees were the araucarias and other gymnosperms which 
dominate, together with the cycads, nearly all the Meso¬ 
zoic landscapes. The cycads became most prominent. 
They varied a great deal in appearance. Some looked 
like our modern cycads, with their short stems and fern- 


79 



FERNS, FOSSILS AND FUEL 


like fronds, while others were more like shrubs. There 
were other gymnospermic trees related to the present-day 
conifers, and the strange looking maidenhair tree, the 
Ginkgo biloba , must have given a peculiar charm to the 
forest. This tree, which probably already existed in 
Paleozoic times, is a complete anachronism, for it still 
is found living today. It defies evolution. Time has 
never changed it. It probably existed in more species 
when it grew wild than it does now, for in recent times 
it has been growing only under cultivation, as a decora¬ 
tive tree in the temple gardens of Eastern Asia. It has 
been imported into America and Europe from the East 
and is now growing in many parks and botanical gardens. 
Some magnificent specimens, standing in the Missouri 
Botanical Gardens at St. Louis, show themselves perfectly 
able to withstand the severe North American winters. 

The Triassic landscape was also rich in ferns and horse¬ 
tails, but they were no longer the same ferns and the 
same horsetails as those that grew in the Pennsylvanian 
period. A type of horsetail was prominent which stands 
midway between the gigantic Pennsylvanian Catamites 
and the modern Equisetum; botanists call it Neocalamites. 
A tongue-shaped fern called Taeniopteris was common. 

The climate during Triassic times was warm and still 
locally dry, but swamps had again become numerous in 


80 



THE ADVENT OF FLOWERING PLANTS 


many places. In consequence, we have some coal seams 
dating from this period. 

Reptile life reached a high level in the Triassic period. 
The Mastodonsaurus giganteus, a fat enormous crocodile, 
inhabited the swamps, and the sand banks beside the 
rivers saw other great crocodiles with spoon-shaped snouts 
called belodons. The dinosaurs were beginning to ter¬ 
rorize the other animals, though they had not yet reached 
their highest development. The earliest known mammals 
appeared. They looked somewhat like the duckbill of 
Australia, the only living mammal which still lays eggs. 

The changes which went on during the Triassic con¬ 
tinued through the Jurassic period. The vegetation be¬ 
came very rich once more, although it did not differ 
much except in details. Animal life now marked the 
highest point in the development of the reptiles. 

A very famous locality of Jurassic deposits is found 
near Solenhofen in Bavaria. The period got its name, 
however, from the Jura Mountains which form the boun¬ 
dary between Switzerland and France, where the charac¬ 
teristic rocks of the period—the type formation—were first 
found and described. The Rock of Gibraltar is entirely 
composed of beds of Jurassic limestone. 

The beds at Solenhofen early became famous for the 
lithographic stone which was secured from the quarries 


81 



FERNS, FOSSILS AND FUEL 


of the region. In this stone, a rich fossil plant and animal 
life has been brought to light. The plant fossils are of 
a gymnospermic type, called Auraucaria, that is still an 
important tree in the floras of the southern hemisphere. 
Gingko trees and a conifer resembling the present-day 
yew tree, also were found. There were many ferns, but 
the most important trees were undoubtedly still the cycads. 

Enormous reptiles populated the Jurassic forests, and 
small mammals were still hiding from them. The air 
also was populated. The earliest bird, the Archaeopteryx , 
flew from tree to tree, probably still clumsily. When it 
settled down to feed on the berries of the cycads, it used 
not only its feet but the claws with which its wings were 
armed. Then, too, unlike modern birds, it had teeth 
in its jaws. The real rulers of the air were the enormous 
flying reptiles, big as aeroplanes, which flew, like bats, 
with the help of a membrane between their front and 
hind legs. 

Insect life also became manifold. A big fly with beau¬ 
tiful wings almost like those of a butterfly and with a 
wing-spread of almost ten inches, named the Kalligramma 
Haeckeli, has been found in the lithographic slate of 
Solenhofen. This developing insect life had a great 
influence on the plant life; the first two flowering plants 
we know appeared in the Jurassic period. Certain types 


82 




Landscape of Pennsylvanian Age (after Potonie). 






















































FERNS, FOSSILS AND FUEL 


of cycads also had developed something like big flowers, 
although they cannot be considered as true flowering 
plants. What the color of the cycads and of the two 
flowering plants (angiosperms) was, it is impossible to 
say positively. Since the insects of the period were at¬ 
tracted by the flowers and helped their pollination, we 
must take it for granted that bright colors like red, blue, 
and white, were represented in the Jurassic forests. 
Nevertheless, the angiosperms were just bginning. They 
do not come into their own until much later, in the Upper 
Cretaceous period. 

The early Jurassic climate may have had seasonal 
variations, for we find annual rings in the fossil woods 
from that time. The climate of the main part was warm 
and uniform, and the fossil woods have no annual 
markings. 

The next period, the Cretaceous, is divided into two 
distinct sections. The Lower, or earlier Cretaceous, is 
much like the Jurassic, so far as flora and fauna are con¬ 
cerned. Some of the finest fossil cycad trunks were found 
in the Lower Cretaceous rocks of the Black Hills in west¬ 
ern South Dakota. At the end of the Lower Cretaceous, 
a great change suddenly took place. The angiosperms, 
or true flowering plants, suddenly overran the vegetation 
of the earth. Just as the migration of the Teutonic na- 


84 



THE ADVENT OF FLOWERING PLANTS 


tions destroyed and overran the Roman empire, the flow- 
ering plants, with an almost explosive expansion, took 
possession of the surface of the earth and established them¬ 
selves as the dominant type, a supremacy which they have 
held to our own day. 

We can reconstruct an Upper Cretaceous flora from 
the Dakota sandstone deposits in Kansas. The type for¬ 
mation of the period is in South Dakota, hence the name, 
but the deposits are much more extensive in Kansas. 
The flora of the period was a sub-tropical one such as 
we see today near the Mississippi delta or in the West 
Indies. Most of the genera which grew then are rep¬ 
resented in the living flora of today, but by other species. 
Magnolias, tulip trees, myrtles, viburnum, oaks, beeches, 
elms, sassafras, and a great variety of Ficus, of which 
the best known living representatives are the fig and rub¬ 
ber trees, were all prominent. There were sweet gums 
and sycamores, and many primitive and now extinct 
angiosperms. 

We know from this horizon only the trees and shrubs. 
We are not familiar with the small plants growing in 
the meadows and forming the undergrowth of the forests. 
Only the organs that fell from the trees and bushes had 
a chance to be imbedded in the sand which later became 
sandstone and so beautifully preserved even the finest 


85 



FERNS, FOSSILS AND FUEL 


venation of the leaves. The grasses, wild flowers, and 
small shrubs did not shed leaves, but withered and 
decayed on the spot. They were therefore unable to 
supply us with fossils. There are only a few seeds and 
flowers known from that time, and occasionally the leaves 
of water lilies which had been buried in the mud. 

With the Upper Cretaceous period, we are able, for 
the first time, to connect the plant life directly with that 
of our own day, because it is so closely related to the 
floras growing at present. The Cretaceous flora as well 
as the later floras of the Tertiary period can best be 
studied by starting from our present vegetation and fol¬ 
lowing the successive horizons downward. When we 
were dealing with the Paleozoic and Mesozoic plant 
life, we had to follow the opposite method and take as 
a starting point the Devonian period in the Paleozoic 
era and the Triassic period in the Mesozoic, and study 
the successive floras in an upward direction from earlier 
to later. But the paleobotanists who specialize in Upper 
Cretaceous and Tertiary plants work from the living 
types down to the earlier because of the close relation 
between them. 

The animal life of the Upper Cretaceous period, how¬ 
ever, was still distinctly Mesozoic. The animal change 
did not come until the following period. Gigantic rep- 


86 



THE ADVENT OF FLOWERING PLANTS 


tiles filled the land, the water, and the air. Enormous 
turtles inhabited the swamps; and one of the most gigantic 
reptiles of all times, the Tyrannosaurus, preyed upon all 
the smaller animals. But the great age of the reptiles 
was drawing to a close, and their grotesque forms began 
to foreshadow somewhat the later mammalian types of 
rhinoceros, elephant, kangaroo, and whale. Enormous 
pteranodons flew in large numbers over the land and sea, 
and great water-reptiles sped like living torpedo boats 
through the oceans. Bird life developed to a still higher 
degree and invaded the water. There were some swim¬ 
ming birds that could not fly, much like the modern pen¬ 
guin. Mammals became more numerous and larger. 
They developed into a menace to the reptiles by eating 
their eggs and thus decimating their offspring. 

The Upper Cretaceous forest in Kansas must have 
been a lively place, filled with many colored flowers, but¬ 
terflies, and bees, and shaking with the steps of the 
heavy reptiles. It could not have been very unlike our 
own forests, although more luxuriant than anything except 
our tropical jungles. The climate was warm and uniform 
throughout a wide range of latitude. Palms grew even as 
far north as Greenland and Spitzbergen. 

It was probably due to the rapid development of insect 
life that the flowering plants spread so suddenly. Butter- 


87 



FERNS, FOSSILS AND FUEL 


flies and bees, in their anxiety to sip the nectar from 
flowers, carry the small amount of pollen that is sufficient 
to fertilize a plant, from the stamens of one flower to the 
pistils of another. Without this help, the flowering plants 
could never have reproduced themselves on a large scale, 
for wind pollination, on which they had been dependent 
before the insects became numerous, is extremely wasteful 
and inefficient. And since the insects are mainly attracted 
by the gay colors and aromatic odors of the flowers, we 
must assume that the trees, shrubs, and herbs of that 
time were beautiful in color and strongly perfumed. 


88 



SIX 


PLANT LIFE IN THE GREAT ICE AGE 

E ARLY Tertiary plants were similar to those of the 
Upper Cretaceous. But later a gradual cooling 
of the temperature set in. Throughout the Middle and 
especially the late Tertiary period, the plant life assumed 
an aspect reminding us of that of northern California 
and Oregon today. 

During the early Tertiary there flourished a sub-tropical 
flora on the west coast of Greenland. It contained ferns 
and cypresses, sycamores, magnolias, sweet-gums, maiden¬ 
hair trees, and many other sub-tropical plants. It resem¬ 
bled the vegetation which grows now in the South of 
the United States and in southern California. Other 
Eocene floras are known from the Gulf coast, Mexico, 
and southern Colorado. They contain palms, figs, laur¬ 
els, and cinnamon, bread-fruit trees, and various cypresses 
and ferns. It was a vegetation indicating a warm climate 
and rather uniform floras over the earth. Similar floras 
are also known in many European countries. 


89 


FERNS, FOSSILS AND FUEL 


The early part of the Tertiary period is called the 
Eocene. It was followed by the Miocene, which fills the 
middle portion of the Tertiary. It was a period of great 
volcanic activities in North America, Europe, and Asia. 
The southern Alps and the Himalayas were formed dur¬ 
ing the Miocene, and the Rocky Mountains were raised 
from a much lower to their present high level. During 
the period great volcanic eruptions took place in the 
western portion of North America, mainly in Washington 
and Oregon. A great many plants were buried in the 
lava and the outlines and venations are beautifully pre¬ 
served in the volcanic tuffa. 

Near the town of Florissant, Colorado, is one of the 
richest fossil plant deposits of the Miocene. At that 
time a small lake existed there in the midst of granite 
hills. At the bottom of this lake a deposit of thin shales 
was formed, largely of volcanic ashes. Many thousands 
of plant fossils, belonging to at least two hundred and 
fifty species, have been found there, as well as thousands 
of insects, remains of fishes, feathers of birds, and shells. 
When we restore the vegetation which lies buried in the 
Florissant shales, we find a large variety of plant types 
ranging from small mosses to the largest trees of the 
time. Conifers like the pine and the juniper were con¬ 
spicuous. There flourished, along the shores of the 


90 



THE ADVENT OF FLOWERING PLANTS 


lake, poplars, myrtles, ashes, holly trees, hickories, wal¬ 
nuts, oaks, maples, elms, persimmons, lindens, wild grapes, 
wild currants, roses, locusts, and a number of other trees 
related to a variety of living forms, even to our peaches 
and hornbeams. Other basins, resembling the one at 
Florissant, occur in the Middle and Upper Tertiary 
formations on the Pacific coast near Spokane; another 
is the John Day basin of western Oregon. 

Similar floras existed throghout the period all over 
Europe, Asia, and even the Arctic. It is a strange sight 
to see fossils of palm trees, laurels, and cinnamons which 
have been dug out from the snowfields of the North. 

The second great period in the formation of coal occurs 
in the Middle Tertiary. The vast lignite and brown coal 
deposits all over the world were laid down in that time. 
Conditions must have been very similar to those of the 
Pennsylvanian period, for both resulted in a climax of 
coal deposition on the earth. 

The fauna which populated the semi-tropical forests 
of the middle Tertiary closely resembled that of the 
tropics today. Gigantic elephants, rhinoceri, and hippo¬ 
potami roamed through the forests, and many birds 
flashed among the trees. Nature was superabundant, and 
the world must have been a much more beautiful one 
than that in which we are now living. 


91 



FERNS, FOSSILS AND FUEL 


During the Middle Tertiary a subtropical flora covered 
Europe. It was a cosmopolitan type of vegetation which 
contained a great many floral elements that are now 
found in Asia, Australia, North and South America, 
and Africa. Not since Pennsylvanian times was there 
such a uniformity of vegetation all over the world. This 
flora was abundant, and, in consequence, left great coal 
deposits besides innumerable localities rich in fossil plants. 
It was the second great epoch of plant abundance in 
the history of the earth. We do not know why it hap¬ 
pened that only during the Pennsylvanian and during the 
middle of the Tertiary the plant kingdom was abundant 
and so uniform all over the world. The fossil plants 
of the time indicate a climate which must have been 
warm and moist all over the world. There are innumer¬ 
able beds of Middle Tertiary plants found close to the 
north pole, and we are forced to accept a warm climate 
for that time throughout the Arctics. 

During the closing epoch of the Tertiary period, we 
notice a lowering of temperature over the northern hemi¬ 
sphere, and an approach to the vegetation that exists 
now in North America, especially in the Pacific states. 
Late Tertiary floras are also known from Europe and 
Eastern Asia. All indicate a tendency to cooler climate 
and a southward migration of plant life. 


92 




Landscape of Triassic Age, reconstructed in Stuttgart. 


























FERNS, FOSSILS AND FUEL 


Toward the end of the Tertiary, great mountain ranges 
were raised by a shifting in the earth’s crust. The yearly 
temperature, which had been slowly cooling, sank more 
rapidly until, during the glacial epoch, an enormous 
ice shield accumulated, covering a large part of North 
America, Northern Europe, and Northern Asia. The 
glacial epoch consisted of several advances and several 
retreats of the great ice masses; at the times of retreat the 
climate became warmer, only to grow cold again when the 
ice came back. These warm periods we call inter-glacial 
epochs and the cold ones glacial epochs. 

We must conclude, however, that it was warmer dur¬ 
ing some of the inter-glacial epochs than it is now. For 
fossil wood of the Osage orange, which does not now 
grow wild north of Tennessee, has been found near 
Toronto in an inter-glacial formation. It has been ob¬ 
served in Finland that certain plants are retreating south 
again, which would indicate a cooling of the present 
climate. This gradual decrease in yearly average tem¬ 
perature has not been measured by scientific observation, 
but it must exist there. Perhaps we are not in a post¬ 
glacial epoch but in an inter-glacial one. Ten thousand 
years from now ice may cover Chicago, and much of 
the existing life of North America and northern Europe 
may again be driven south. 


94 



PLANT LIFE IN THE GREAT ICE AGE 


The Danube valley near Vienna was not covered with 
ice during the glacial epochs, but lay open between the 
ice masses of northern Europe and those which capped 
the Alps. From deposits in this valley, we can recon¬ 
struct the flora which probably grew during the glacial 
age where Vienna now stands. This flora has been 
studied and its appearance described as alpine. Arctic 
plants of today and those of the Alps have much in com¬ 
mon with those of the glacial period. In the soil which 
was free from ice, there grew, during the summer, a 
vegetation reminding us of the Alps and of the Arctic. 
There were such types as the rhododendron, the violet, 
the primrose, the cinquefoil, the saxifrage, and the fleece 
flower. The trees were small pines, birches, beeches and 
rather crippled and dwarfed oaks. Among these plants 
and trees walked gigantic elk and bison, the hairy ele¬ 
phant, rhinoceri, and early man. It was not a pleasant 
climate, like that of the earlier Tertiary and Cretaceous 
times, but the surface of the earth was a great deal more 
impressive, with great mountain ranges towering above 
it. It is a peculiar coincidence that whenever the climate 
is warm and uniform over the earth, the relief is rather 
flat and uninteresting. It is apparently as true in Na¬ 
ture as in human life that we never can have all that 
we would like. 


95 



FERNS, FOSSILS AND FUEL 


When the glaciers retreated, for what may or may 
not be the last time, the arctic plants retreated with them 
toward the north, and the alpine plants moved up into 
the higher altitudes which had become free from eternal 
ice. The plains of Europe received back some of the 
exiled plants from the south. But as has been explained 
before, conditions for a return were different in Europe 
with its east-west mountain barriers and the Mediter¬ 
ranean Sea cutting it off from Africa and Asia Minor 
than they were in North America where there is no 
Mediterranean and the mountain chains run north and 
south. Thus, as we have already seen, though the floras 
of Europe and North America were identical in the 
Tertiary period, they became differentiated after the 
glacial epoch. 


96 



SEVEN 


PLANTS AND MAN 

D URING the glacial epoch, a new factor was intro¬ 
duced into the evolution of plants. Slight at 
first, it increased more and more as time went on, until 
in our own day it has become of truly revolutionary sig¬ 
nificance. Its effect upon the life of the plant kingdom 
is comparable to that of the differentiation effected by 
climates. 

Man’s influence upon plants has been both destructive 
and constructive. On the one hand, he has destroyed 
most of the great primitive forests of North America, 
of northern Europe, and of China, and he has seriously 
reduced even some of the luxuriant African forests. 

Many of these areas formerly covered by majestic 
forest trees man has replanted with orchards and with 
cultivated fields of grain and vegetables; and in numer¬ 
ous instances the plants that he cultivates have been 
brought long distances from their native soil. Most of 
the cereals, vegetables, and fruits that are now grown 


97 



FERNS, FOSSILS AND FUEL 


widely in America came originally from Asia or Europe; 
while the Western Hemisphere, in turn, has made a 
number of plant contributions to the Old World. 

These humanly controlled migrations of food plants, 
of which some of the more important examples are noted 
in this chapter, have constituted an important economic 
factor in the history of civilization. 

The plants that now, under intensive cultivation, sup¬ 
ply the great bulk of the world’s food, are all descendants 
of the primitive flowering plants that first made their 
appearance so inconspicuously in the Jurassic period, 
millions of years ago, when the cycads dominated the 
landscape. 

The ancestors of our modem food plants were scraggly 
things with small, uninviting fruit, which would be of 
little commercial value today. Under cultivation through 
many centuries they have become transformed so that 
they now bear little resemblance to the wild plants from 
which they are descended. 

In recent years, marvelous improvements in all kinds 
of food plants, and even the creation of entirely new 
varieties, have been made possible by scientific selection 
and interbreeding. The work of the late Luther Burbank 
in this field has produced spectacular results. Splendid 
new types of wheat and corn have been produced, which 


98 



PLANTS AND MAN 


are not only superior in quality and quantity of the crop, 
but are also immune to plant diseases and fitted to thrive 
under climatic conditions which formerly had been un¬ 
favorable to the prosperity of the plants. 

This scientific control of plant evolution, of far-reach¬ 
ing importance in its economic aspects, is based upon 
knowledge of the laws of genetics and the transmission 
of hereditary characters, which began with the experi¬ 
ments of Gregor Mendel, in a monastery garden in 
Austria, about fifty years ago. He blended different 
varieties of sweet pea, and worked out the laws governing 
the appearance of hereditary traits in their offspring. 
These laws have been found to be applicable not only 
to plant but also to animal life. 

Let us glance, now, at some of our well-known friends 
of modern orchards, grain fields, and vegetable gardens, 
and see how far they have wandered from their original 
homes, at the bidding of man. 

Wheat (Triticum rulgare) and Hard Wheat ( Triti - 
cum durum) : There are a number of species of wheat, 
of which these are the most important, under cultivation 
in different parts of the world. Wheat originated per¬ 
haps in Mesopotamia or in Egypt; a small, wild wheat 
still grows in parts of Asia Minor. The cultivation of 
wheat extends far back into prehistoric time. It was 


99 



FERNS, FOSSILS AND FUEL 


the most common cereal of antiquity. It was well known 
to the ancient Egyptians, and grains of it have been 
found with their mummies. It has been raised more 
or less successfully over the entire temperate portion of 
the Old World, and was introduced into the New World 
soon after the discovery of America. 

Barley ( Hordeum distich on) : Barley is among the 
most ancient of cultivated plants. It originated in the 
Old World and is now grown successfully in all temper¬ 
ate lands. There are several species besides Hordeum 
distichon. 

Rye ( Secale cereale ): Rye is comparatively new as a 
cultivated cereal. It has not been under cultivation exten¬ 
sively many centuries, unless perhaps in Russia. The an¬ 
cient Greeks were not acquainted with it. In Rome it 
became known about 100 A. D. An Old World plant, 
it is now at home in the New as well. 

Oats ( Arena sativa): This cereal, popular mostly 
among horses, was known to the ancient Greeks and 
Romans, but does not appear to have been known in 
China until about 900 A. D. It, too, quickly made itself 
at home in the New World. 

Millet ( Panicum miliaceum) : This is one of the minor 
cereals. The cultivation of the plant goes back to pre¬ 
historic times in the south of Europe, in Egypt, and in 


100 



PLANTS AND MAN 


Asia. Like other Old World grains, it has followed the 
European migration into the New World. 

Rice (Oryia sativa) : This important cereal is a native 
of the Far East, where it has been used from time imme¬ 
morial for the support of large populations. It was not 
known to the Greeks or the Romans. It probably was 
introduced into Europe by the Portuguese in the days of 
Vasco da Gama, and it is raised in Spain and Italy. 
In America it has been cultivated chiefly in Louisiana, 
around the delta of the Mississippi. 

Maize ( Z.ea mays) : Maize, popularly known in the 
United States as corn, is a 100 per cent American plant, 
native to the Western Hemisphere. It was cultivated by 
the Indians, and after the discovery of America it was 
quickly introduced into the Old World. In Europe it 
is widely known as Turkish wheat , and many persons 
therefore erroneously suppose it to be of Turkish origin. 
It appears that the first seed grains were sent from America 
in the year 1500 to Seville, in Spain. The plant is now 
cultivated throughout the warm temperate regions of 
Europe and Asia, its widespread diffusion being very 
rapid. At the time of the discovery of the Americas, maize 
was a staple food product throughout both continents. 
Its cultivation must have been of very ancient origin, 
for it has never been found growing in its wild state. 


101 



FERNS, FOSSILS AND FUEL 


Cotton ( Gossypium herbaceum) and Tree Cotton 
(Gossypium arboreum ): Cotton, though mainly valu¬ 
able as raw material for clothing, also yields a valuable 
food oil from its seeds. The herbaceous type was culti¬ 
vated in ancient Persia, where the observant Greeks noticed 
it at the time the of the expeditions of Alexander. Al¬ 
though the southern United States has become the greatest 
cotton growing region in the world, the plant does not ap¬ 
pear to have been introduced into America until long after 
the discovery of the New World, coming probably from 
southern Europe. As late as the year 1774, only two 
years before the Declaration of Independence, a bale 
of American-grown cotton was confiscated at Liverpool 
on the ground that the cotton plant did not grow in 
America. 

The tree cotton is a native of tropical Africa, and 
appears to have been known to the Romans in the time 
of the Empire. 

There is, however, a purely American branch of the 
cotton family. This is the Barbados cotton ( Gossypium 
barbadense) . At the time of the discovery of America, 
the Spaniards found it under cultivation, from the West 
Indies to Brazil and from Mexico to Peru. 

Coffee ( Coffea arabica) : To this plant the world is 
indebted for its most popular breakfast beverage. Ap- 


102 



PLANTS AND MAN 


parently it is of African origin; it still grows wild in 
Abyssinia and in the Sudan, but notwithstanding its 
name it has never been found growing indigenously in 
Arabia. But the Arabs apparently were the first to 
appreciate the value of the coffee bean. By the fifteenth 
century, the Arabs were drinking fragrant coffee, and 
by the end of the seventeenth century the coffee bean was 
introduced into western Europe. The popularity of the 
new beverage may be judged by the rapid multiplication 
of “coffee houses” in London and other European cities. 
The first coffee plants grown in America were planted by 
the Dutch at Surinam (Dutch Guiana) in 1718. The 
plant thence made its way to the French West Indies, 
reaching Martinique in 1720 and Guadeloupe in 1730. 
Since then it has spread widely through the tropics of 
America and Asia, Brazil and Java being important cen¬ 
ters of cultivation. In tropical agriculture, coffee takes 
the place occupied by the grape in Europe and the tea 
plant in China. 

Potato (Solatium tuberosum) : The potato is perhaps 
the most valuable plant gift from the New World to the 
Old. When Columbus reached America, the cultivation 
of the potato was practised, with every appearance of 
ancient usage, in regions of temperate climate from Chile 
to Mexico, whence it spread northward to the regions 


103 



FERNS, FOSSILS AND FUEL 


now known as Virginia and North Carolina. The potato 
plant still grows wild in Chile, in a form clearly showing 
its close relationship to its cultivated cousins. The Euro¬ 
pean colonists quickly recognized the merits of the potato. 
It was first imported into Europe between 1580 and 1585, 
at first by the Spaniards and later by the English, at the 
time of Raleigh’s voyages to Virginia. The potato soon 
became one of the most important food plants in various 
countries of northern Europe, particularly in Ireland, 
whence the misleading term Irish potato . 

Sweet Potato (Ipomaea batatas): This plant also is 
undoubtedly of American origin, but not related to the 
common potato. When Columbus, on his return to Spain 
from his first voyage, offered her various products of 
the new lands he had discovered, sweet potatoes were 
included among them. The cultivation of this plant in 
Spain dates from the beginning of the sixteenth century. 

Tobacco (Nicotiana tabacum) : While tobacco is not 
a food, it has, in the form of the after-dinner cigar, so 
close a relationship with dining, that some reference to 
the tobacco plant will be appropriate at this time. When 
Columbus made his well-known discovery in 1492, the 
custom of smoking and of chewing tobacco, as well as 
that of snuff-taking, was diffused over the greater part 
of this continent. It appears that the inhabitants of South 


104 



PLANTS AND MAN 


America did not smoke; they chewed tobacco or took 
snuff. In North America, however, from the Isthmus 
of Panama and the West Indies, as far as Canada and 
California, the custom of smoking was universal. It 
was the symbol of peace. 

Though the various Asiatic and European peoples are 
now great lovers of tobacco, none of them were acquainted 
with it before the discovery of America. At the begin¬ 
ning of the seventeenth century the tobacco plant was 
introduced into Turkey, the Persians soon afterward re¬ 
ceiving it from the Turks. John Nicot, from whom the 
plant gets its scientific name, saw it in Portugal in 1560. 
The Portuguese probably introduced it into India, where 
they were very influential at that time. 

Sugar-Cane (Saccharum officinarum ) : The sugar¬ 
cane is cultivated now in most of the warm regions of 
the globe. Various historical facts indicate that it was 
first grown in southern Asia, whence it spread into Africa 
and later into America. It originated probably in India, 
Cochin China, or the Malay archipelago. The Arabs 
in the Middle Ages carried it into Egypt, Sicily, and 
southern Spain, where it flourished widely until the com¬ 
petition of colonial sugar caused its cultivation to be 
abandoned. Don Henriquez transported sugar-cane 
plants from Sicily to the Madeira Islands, whence they 

105 



FERNS, FOSSILS AND FUEL 


were taken to the Canaries in 1503. It was from there 
that the sugar-cane made its way to Brazil at the begin¬ 
ning of the sixteenth century. It reached Santo Domingo 
about 1520, and soon afterwards made itself at home 
in Mexico. By 1644 it was being raised in Martinique, 
and by about 1650 in Guadaloupe. In the United States, 
it has been raised successfully in Louisiana. 

Pumpkin (Cucurbita pepo): The ancestry of this 
succulent vegetable is somewhat uncertain. Botanical in¬ 
dications suggest a Mexican or Texan origin. But a 
related species (Cucurbita maxima ) was known to the 
Romans and to the people of the Middle Ages in Europe. 

Melon (Cucumis melo) : This is another garden friend 
of uncertain origins. Its cultivation may have begun 
independently in India and in Africa. Its introduction 
into China does not seem to antedate the eighth century 
of our era. The ancient Egyptians apparently were not 
acquainted with it. It was introduced into the Graeco- 
Roman world, probably in the days of the Empire, at 
the beginning of the Christian era. 

Watermelon (Citrullus ml gar is) : Though now a 
healthy naturalized American, the watermelon is, perhaps 
appropriately, of African origin. It is indigenous to the 
tropical part of that continent, on both sides of the 
equator. The ancient Egyptians esteemed and cultivated 


106 



PLANTS AND MAN 


it. Europeans introduced it into the Western Hemis¬ 
phere, where it now flourishes under proper climatic 
conditions, from Chile to the United States. 

Cucumber (Cucumis satirus) : This humble friend in 
our kitchen gardens can boast a respectably long lineage. 
It was known to the ancient Hebrew, as well as to the 
Greeks and the Romans. It has been cultivated in India 
for at least three thousand years. 

Wine Grape (Vitis vinifera): This is an extremely 
ancient plant. During the Miocene or Middle Tertiary 
period, species related to the wine grape were widely 
distributed throughout Europe and North America; they 
flourished in Iceland, in Greenland, and in far-away 
Japan. The glacial epoch drove them south, but with 
the return of a warmer climate the wild grape moved north 
again, crossing the Alps and the Caucasus. 

The cultivation of the grape goes back to early antiq¬ 
uity. We find grape wine in common use in Homers 
time. The production of fermented grape juice evidently 
originated with the Semitic peoples who lived in Meso¬ 
potamia and Palestine. From the Semites the Greeks 
learned the art of wine-making, and passed it on to the 
Romans. It spread from Italy to Spain, France, Ger¬ 
many, and the British Islands. Grape culture has been 
carried into nearly all lands where a mild climate prevails, 


107 



FERNS, FOSSILS AND FUEL 


though the plant grows best in the Mediterranean coun¬ 
tries of Europe and Asia. The Norse discoverers of 
America called the new country Vinland, because of the 
abundance of wild grapes that they found growing there. 

Fig (Ficus carica ) : Judging from the presence of fos¬ 
silized fig leaves in the Tertiary formations of western 
Asia and from their absence in the Tertiary of Europe, 
we may conclude that the fig tree originated in Asia and 
spread westward. Throughout antiquity the fig, together 
with the wine grape and the olive, was the best known 
and most highly appreciated plant. It is frequently mem- 
tioned in the Bible. Its real home-land is now the Semitic 
Near East. There it grows best and produces its sweetest 
fruit. It was not known in Greece at the time of the 
Trojan war, but we find it mentioned in the Odyssey . It 
flourishes wild, or nearly so, from Persia to the Canaries, 
on both sides of the Mediterranean. 

Cherry (Prunus cerasus): This luscious fruit has a 
long- history. The wild cherry still is found in Trans¬ 
caucasia, and its sweet variety must have been cultivated 
in the region where stood the ancient city of Cerasus, in 
Asia Minor, whence it took its name. It is said that the 
cherry was introduced into Rome by the gourmet Lucullus, 
Roman Consul in the first century B. C., who destroyed 
the city of Cerasus. From Italy the cultivation of the 


108 



PLANTS AND MAN 


sweet cherry spread all over Europe, and into all the 
temperate regions of the Old and the New World. 

Apple (Pyrus malus) : This most familiar and popular 
of all our orchard fruits has a history reaching into the 
mists of antiquity. Whether or not it was the fruit that 
tempted Eve in the Garden of Eden, we know that the 
Lake Dwellers of Switzerland and Italy gathered wild 
apples in great quantities. It still grows wild throughout 
Europe, Asia Minor, and Persia. The colonists lost no 
time in introducing the cultivated varieties into America, 
where a wild crab-apple was indigenous. 

Pear (Pyrus communis) : The pear, a cousin of the 
apple, has a rather similar history. It still grows wild 
over the whole of temperate Europe and western Asia. 
The mural paintings of Pompeii frequently represent this 
tree- with its fruit. The finer cultivated varieties came to 
America with the apple. 

Plum (Prunus domestica) : The plum seems to have 
come from the Near East; it still grows wild in Asia 
Minor and northern Persia. It was early appreciated by 
mankind, and was introduced into Europe probably about 
two thousand years ago. 

Apricot (Prunus Armeniaca ): This relative of the 
plum seems to have made a far longer journey to reach 
us. The Chinese were familiar with it two or three thou- 


109 



FERNS, FOSSILS AND FUEL 


sand years before the Christian era. Its native home no 
doubt was in far eastern Asia. 

Peach ( Amygdalus persica) : The ever-popular peach 
is another traveler, probably, from distant China, reaching 
Europe through Persia. The Greeks and the Romans 
adopted it into their orchards shortly after the begin¬ 
ning of the Christian era. 

Almond ( Amygdalus communis ): This is a cousin 
of the peach, but esteemed for its kernel rather than for 
its fruit. It appears to be a native of northern Africa. 
It was known to the ancient* Hebrews, and we see it pic¬ 
tured in the wall frescoes at Pompeii. 

Walnut ( Juglans regia) : The walnut has long been a 
favorite among the nut-trees. Before the glacial epoch, 
the walnut was common in North America and in Europe. 
It became extinct in Europe, because of the glaciation, 
but it continued to flourish in North America, as well 
as in Asia Minor, among the mountains north of India, 
in Burma, and in Japan. In classical times it was brought 
back to Europe. The Greeks secured from Persia an 
excellent variety of the tree and passed it on to the Romans. 
In India it had become domesticated as early probably 
as 150 B. c. 

Olive ( Olea europaea) : This is a much beloved tree 
of the ancient peoples. It is mentioned in Genesis, and 


110 




Cycad Tree (after C. ]. Chamberlain s “The Living Cycads.”) 
Used by permission of the University of Chicago Press . 





FERNS, FOSSILS AND FUEL 


was one of the goodly trees promised to the Hebrews in 
the land of Canaan. The Egyptians cultivated it, and 
the Iliad and the Odyssey speak of olive wood and olive 
oil. In later times, the Romans were familiar with the 
tree. In 1403 we find allusions to it by the early voyagers 
to the Canary Islands, where it may have been introduced 
by the Phoenicians. In the United States the olive has 
found a congenial home in California; the first trees were 
planted by the monks at the Mission of San Diego, in 
the far southern part of the State. 

Tomato (Lycopersicum esculentum) : The tomato has 
come into popularity during comparatively recent years. 
It is another of our sturdy native American plants, un¬ 
known in Europe before the discovery of America. It is 
probably of Peruvian origin, at least as a cultivated 
plant, though the name is of Mexican origin, derived 
from the Aztec tomatl. It is now a familiar garden 
plant throughout the United States, and from the West 
Indies it was introduced into Europe. 

Avocado or Alligator Pear (Persea gratissima) : This 
fine fruit, still not very widely known, is also an Ameri¬ 
can product. It has been found growing wild in forests, 
on the banks of rivers, and along the sea-shore, from 
Mexico southward to the Amazon and throughout the 
West Indies. In the time of Columbus it was already 


112 



PLANTS AND MAN 


being cultivated in Mexico and Peru. Introduced into 
Spain about 1600, it spread to India and other tropical 
and subtropical countries of the Old World. 

Date Palm ( Phoenix dactylifera) : This beautiful tree 
has flourished from prehistoric times in the warm, dry 
zone extending from the west coast of Africa to northern 
India. Since the days of ancient Egypt and Babylonia 
it has been cultivated, and its natural area has remained 
much the same. 

Pineapple ( Ananas satira) : This savory fruit is 
another American contribution to the tables of the world. 
Nana was the Brazilian name, which the Portuguese 
turned into ananas , the name by which it is still com¬ 
monly known in Europe. The Spaniards, however, called 
it pinas, whence the English name pineapple . It was in¬ 
troduced into Asia and Africa at an early date by Euro¬ 
peans. A specimen of the fruit was brought to Charles 
V, who mistrusted its strange appearance and declined 
to taste it. It has been found growing wild in the warmer 
regions of Mexico, as well as in the vicinity of Panama, 
in Guiana, and in the Brazilian province of Bahia. It 
probably was first cultivated in the subtropical districts 
of the United States in 1850. There are now immense 
plantations of pineapples in the Hawaiian Island. 

Lemon ( Citrus limonia) : This acid but valued fruit 


113 



FERNS, FOSSILS AND FUEL 


came originally from southern Asia. It seems to have 
been unknown to the Romans of the classic period, but 
must have been familiar to the Hebrews. The Greeks 
first became acquainted with it in Media and Persia. 
The Arabs extended its cultivation into northern Africa 
and southern Europe. We find it first mentioned in 
Italy in the year 1260. In the United States it has taken 
root in Florida and California. 

Sweet Orange (Citrus aurentium) : This most attrac¬ 
tive of citrus fruits has wandered far from its early home, 
for it seems to have come from southern China or Cochin 
China, or possibly India. From India the ever-industrious 
Arabs brought it to Palestine, Egypt, and the east coast 
of Africa. Today, of course, the word orange is almost 
synonymous with Florida and California. 

Grapefruit (Citrus grandis) : This is another member 
of the citrus family, which has only very recently made 
its way to our tables. Its origin is uncertain, but it seems 
to have been introduced into Florida by the Spaniards 
in the early part of the sixteenth century. 

Not only has man made desirable transplantations; he 
has also involuntarily carried with him pernicious weeds. 
Plant parasites, such as the Phylloxera , which spread dis¬ 
aster among the vineyards of southern Europe, were 
brought in. Animal pests, like the English sparrow, were 


114 



PLANTS AND MAN 


transplanted to far continents through the mistaken idea 
that they would be a help against insect pests. Rabbits 
were introduced into countries where they had never 
existed and became destructive to cultivation. 

Finally man has created new varieties of fruits and 
vegetables and flowers. Since plants play a highly im¬ 
portant role in the feeding of man and domestic animals, 
great energy and much money are devoted to research 
in agriculture, horticulture, and silviculture. We cannot 
imagine how far-reaching the changes in plant life may 
be, as a result, in the course of the next few centuries. 
Human population is steadily increasing, and starvation 
will ultimately face the human race if it is unable to 
increase its food supply in proportion. If a new glacia¬ 
tion should occur, however, all our calculations would 
be upset and man would probably be impotent against 
the superior power of Nature. 

There is no rest or standstill in the march of evolution, 
and the plant world will change as it has always changed 
in the course of the past hundreds of millions of years. 
Compared with this march of events in a well-nigh endless 
time, our own human observation seems infinitely small. 
Just as astronomy gives us a glimpse of boundless space, 
so the history of the earth and of its flora and fauna 
opens before us a vista of the boundlessness of time. 


115 



EIGHT 


THE ROMANCE OF COAL AND OIL 

F OSSIL plant remains have another interest for us 
in addition to the picture they give us of the world 
as it appeared in former ages. Their close relation to 
coal and to oil, two very important commodities of mod¬ 
ern civilization, makes a knowledge of them highly desir¬ 
able for practical purposes. They are also very valuable 
as indicators of geologic levels or horizons. 

When the geologic formations in some locality are 
studied with the help of type sections, a certain for¬ 
mation or series of formations is usually found to be 
exceptionally well exposed. It is possible to examine in 
such places a consecutive series of sediments which rep¬ 
resent a considerable portion of geologic chronology. By 
the combination and comparison of numerous type sec¬ 
tions, the entire history of Paleozoic, Mesozoic, and 
Cenozoic rocks was established. 

The various horizons of these sections contain plant 
and animal fossils which are characteristic of the sections. 


116 


THE ROMANCE OF COAL AND OIL 


They are called index fossils. With their help it is pos¬ 
sible to compare horizons in distant localities, and often 
to determine to which geologic age the section belongs. 
It is true that the fossil shells and other small marine 
animals that are embedded in limestone and sandstone 
supply many more index fossils than do the plants of 
the shale and the sandstone. The lower animals, or in¬ 
vertebrates, will therefore always be more important for 
historical geology than the plants, but in a number of 
instances, especially in many horizons of the Pennsyl¬ 
vanian and Tertiary periods, plants are the only index 
fossils we know. 

Sometimes it is extremely important to know to just 
which geologic age certain rocks belong. For instance, 
some time ago a petroleum company was drilling for 
oil in Louisiana. The drillers had gone down over four 
thousand feet, and drilling had become very expensive. 
The oil-bearing sands in that particular locality are 
found in the Lower Cretaceous formations. Immediately 
below the Lower Cretaceous rocks are the Pennsylvanian, 
because there the intermediate formations are missing. 
Such a break in the series is called by geologists an un¬ 
conformity. It was of utmost importance for the oil 
company to know whether they were still drilling in 
the Lower Cretaceous rocks or whether they had already 


117 



FERNS, FOSSILS AND FUEL 


reached the Pennsylvanian formations, for the Pennsyl¬ 
vanian in that region does not contain oil pools. A 
chunk of rock taken from the greatest depth of the drill 
hole, the so-called drill core, was shipped to a paleo- 
botanist. He was able to determine from the plant fos¬ 
sils in it that the rock belonged to a certain part of the 
Cretaceous period and not to the Pennsylvanian. So the 
drilling went on. 

The identification of different coal seams is frequently 
made in the same way on the basis of fossil plants, es¬ 
pecially in regions where the coal beds are very much dis¬ 
turbed and twisted, so that the drill core may run through 
the same coal seam several times. This often happens 
in the Ruhr district in Germany and in the Belgian coal 
fields. 

All the coal that we know was produced from swamps 
that had been buried in geologic times under an accumu¬ 
lation of sediments. Therefore, a knowledge of coal goes 
hand in hand with a knowledge of the fossil plants which 
have made it up. In coal geology we distinguish between 
the under clay on which the coal seam rests, the coal bed 
itself, and the roof which immediately overlays it. The 
under clay, as we have already noticed, is the subsoil on 
which the swamp grew; the coal bed is the carboniferous 
material formed from the vegetation of the swamp; and 


118 



THE ROMANCE OF COAL AND OIL 


the roof is the shale, sandstone, or limestone bed formed 
from the mud, sand, and lime contents carried by the 
waters which inundated and covered the swamp. The 
under clay usually contains innumerable roots; the roof 
frequently bears impressions of leaves, stems, and seeds 
from the vegetation of the swamp; the coal itself, if 
microscopically examined, shows woody fibers, plant 
membranes, and spores. 

As a rule, the coal is very much metamorphosed vege¬ 
table matter which has been subjected to enormous pres¬ 
sure and heat. Many feet of peat and living plants were 
reduced to a very few feet of coal. During the process 
the structure of the plant materials was greatly changed 
and the details obliterated. But occasionally a mineral 
spring was active in the swamp, or the invading waters 
contained a high percentage of silica or lime. Lumps 
of vegetable matter were rapidly saturated with the silica 
or lime and a perfect preservation of the plant tissues 
instead of an amorphic, or formless, carbonization took 
place. Such lumps with their perfectly preserved plant 
structures are found, as we observed in an earlier chap¬ 
ter, sticking out of the coal like raisins from a cake. 

These coal balls, in which we can see under the micro¬ 
scope the anatomic structure of leaves, stems, reproduc¬ 
tive organs, and the smallest components of the plant 


119 



FERNS, FOSSILS AND FUEL 


bodies, show exactly the material out of which the coal 
was formed. The structures thus revealed convince us 
that basic biologic processes existed in Pennsylvanian times 
as they do now, and that plants lived and reproduced 
themselves in the same way then as at the present time. 
There are differences in form but not in principle. 

It has been established that the qualities of our coal 
deposits depend to a large extent on the material from 
which they were made. A coal that was formed from 
wood is different from a coal that contains a large num¬ 
ber of spore remains. The latter is oily, has a larger 
percentage of volatile substances, and is better for oil 
production by low temperature distillation, while the 
former is more suitable for making coke. Such differences 
as these can be determined beforehand by a knowledge 
of the fossil forms that are found in the coal. 

The theory is now pretty generally accepted that most 
coal seams have been formed in situ . In other words, the 
plant material from which they are built up actually 
grew on the spot where the coal seam is. This is called 
autochthonous formation of coal. The other theory, now 
held by only a few geologists, holds that the plant material 
of the coal bed was carried from the original swamps 
by water currents into lake beds and did not grow on 
the spot. This theory is called the allochthonous forma- 


120 



Cross Section through 










































































FERNS, FOSSILS AND FUEL 


tion of coal. We shall probably not be much mistaken 
if we assume that in almost all cases autochthonous for¬ 
mation took place, although, there are few, indeed a very 
few, minor coal beds where an accumulation of plant mat¬ 
ter carried into a water basin is obvious. 

Some petroleum pools probably are due to an accu¬ 
mulation of vegetable oils, but the majority originated 
from the fats of marine animals. Formerly it was gener¬ 
ally assumed that all oil came from animals, but recent 
microscopic examination and treatment under pressure 
and high temperature of the so-called mother rocks of 
oil prove that some of them are full of algal bodies. 

A mother rock is a rock in which the oil originated. 
Usually it is oil shale. High pressure has driven the 
oil out of these rocks into the porous sandstones which 
frequently accompany the mother rocks. The oil moves, 
driven by rock pressure and water pressure, into the 
sandstones, which are called oil sands. The oil currents 
move through these oil sands, and their discovery is 
the great game of the oil companies, whose geologists’ 
job is to find the oil pools, sometimes at depths of seven 
thousand feet. Whenever an oil current in its circula¬ 
tion has been stopped by an impenetrable rock cover, or 
wherever it has moved more freely in a crevice filled 
with very porous material until it is stopped again by 


122 



THE ROMANCE OF COAL AND OIL 


some irregularity of the rocks, there is accumulated, un¬ 
der enormous pressure, an oil pool. It is usually com¬ 
bined with gas and also with salt water. When a drill 
penetrates to this oil accumulation the enormous pres¬ 
sure forces out the oil or gas or the salt water, and we 
have a “gusher.” Sometimes the rocks are folded to 
form a dome which looks more or less like a cup upside 
down, and then there is a splendid chance for the accu¬ 
mulation of oil under the top of the dome, provided 
that mother rocks are sufficiently near to supply the oil. 

There are some great beds in California composed 
of diatomes, which are microscopically small unicellular 
algae, contained in silica capsules. These beds are a 
mass of white powder several miles long and several miles 
thick, lying below the surface of the earth. The oil 
which the living diatomes contained has passed into 
some of the California oil sands which are near by. Deep- 
sea algal accumulations have also produced some of our 
deepest and richest oil pools, formed as the ocean bed 
was filled up with limestone, sandstone, and shale masses. 
These are the sources of the chief vegetable oil pools which 
remain for the world’s use. 

The use of mineral oil has been enormously increased 
during the last decade. The world production up to 
and including the year 1925 amounted to 13,500,000,000 


123 



FERNS, FOSSILS AND FUEL 


barrels, of forty-two gallons each. Of this amount the 
United States has produced over 8,500,000,000 barrels, 
or sixty-three per cent of the total. During the year 
1925, the United States alone produced 759,000,000 bar¬ 
rels. In that year a committee of eleven appointed by the 
American Petroleum Institute made a report on our pe¬ 
troleum resources in order to answer a questionnaire of 
the Petroleum Board appointed by President Coolidge. 

In considering the future supply of crude petroleum, 
the Committee estimated a reserve, in the United States, 
of 3,210,000,000 barrels from present producing wells, 
and 2,111,000,000 from proven but undrilled acreage, a 
total known reserve of 5,321,000,000 barrels. Since this 
report was made, new oil pools have been discovered and 
production has been somewhat decreased. It amounted 
to 408,735,493 barrels during 1929. 

Where are we to turn for dependable oil supplies when 
our domestic oil resources begin to fail? Mexico is to 
be considered first in line, but its production has declined 
from 193,000,000 barrels in 1921 to 113,000,000 in 1925, 
and further since that year. Venezuela and Columbia 
produce large amounts, but much less than Mexico. Ar¬ 
gentina’s supply does not cover her domestic consumption. 

In Europe, the Russian fields have only recently passed 
the peak of 73,000,000 barrels established in 1916. 


124 



THE ROMANCE OF COAL AND OIL 


In Asia, Persia produced about 35,000,000 barrels in 
1925. During that year, India and the Dutch East 
Indies produced together about 30,000,000 barrels, with 
no indication of noticeable increase. 

When domestic production and foreign imports are 
no longer sufficient to meet the American demand for 
petroleum, the deficit will have to be supplied from sub¬ 
stitutes such as alcohol, benzol, oil-shale products, and 
above all, from the low-temperature distillation products 
of coal in recent years. Synthetic petroleum has been pro¬ 
duced from coke and water-gas under high pressure at 
a very high temperature. This process will soon be per¬ 
fected so as to produce commercial quantities at a price 
not too high, at least for countries where oil is expensive, 
as in Germany or England. 

Through the use of coal and mineral oil our generation 
is able to utilize the fuel accumulations of past geologic 
ages. In ancient times, man’s only fuel was furnished 
by wood of living trees. Coal and mineral oil may be 
looked upon as stored solar energy which is released again 
when it is burned to warm our homes and turn the 
wheels of our factories and machines. When we drive 
our motor cars, we rarely think that it is solar energy 
which is harnessed to run the vehicle. But the light from 
the sun was captured by plants which used it to make 


125 



FERNS, FOSSILS AND FUEL 


fats and cellulose and proteins. The plant oils, after 
having been buried for millions of years, are liberated 
by the oil driller, refined into gasoline, and burned in 
the carburetor of an automobile to provide its motive 
power. Even oil of animal derivation is indirectly of 
solar origin, since animals depend on plants for their food. 

Only a limited reservoir of fossil fuel is at the dis¬ 
posal of the human race, but it is so large that our gen¬ 
eration and the next one will not have to bother about 
its exhaustion. Perhaps by the time it is gone, man will 
have discovered other great sources of energy. 

Important as our contemporary vegetation is for our 
well-being, the plants of the past have influenced human 
life to at least as large a degree. They have added 
greatly to its comforts, and have immeasurably increased 
human power. The history of plant life on earth is not 
a matter of purely scientific interest; it is one of great 
practical importance as well. 


126 



GEOLOGICAL PERIODS 


CHRONOLOGY OF EARTH’S HISTORY 

Cenozoic or Recent Era Began about 

Quaternary period 

Recent Epoch 50,000 b. c. 

Pleistocene or Glacial Epoch 1,000,000 B. c. 


Tertiary Period 
Pliocene Epoch 
Miocene Epoch 
Oligocene Epoch 
Eocene Epoch 
Paleocene Epoch 
Mesozoic or Medieval Era 
Cretaceous Period 
Jurassic Period 
Triassic Period 
Paleozoic Era or Antiquity 
Permian Period 
Pennsylvanian Period 
Mississippian Period 
Devonian Period 
Silurian Period 
Ordovician Period 
Cambrian Period 
The Proterozoic Era 
The Archeozoic Era 


7,000,000 b. c. 
19,000,000 b. c. 
35,000,000 b. c. 
55,000,000 b. c. 
short period intervening 

95,000,000 B. c. 
155,000,000 b. c. 
190,000,000 b. c. 

Earth 

215,000,000 B. c. 
250,000,000 b. c. 
300,000,000 b. c. 
350,000,000 b. c. 
390,000,000 b. c. 
480,000,000 b. c. 
550,000,000 b. c. 

Certain Archean works 
have been estimated to 
be 1,500,000,000 years 
old. 


127 



FERNS, FOSSILS AND FUEL 


SOME OF THE BOOKS USED FOR REFERENCE 

Bailey, L. H. Cyclopedia of American Horticulture. 
4 vols. Macmillan Co., New York City. 1909. 

Berry, E. W. Tree Ancestors . A glimpse into the past, 
pp. vi 270. 1 pi. 47 figs. Williams & Wilkins Co., 
Baltimore, Md. 1923. 

Berry, E. W. Paleobotany: A Sketch of the Origin and 
Evolution of Floras. From the Smithsonian report 
for 1918, pp. 289-409, with 6 plates. Washington, 
D. C. 1920. 

Chamberlin, T. C. and R. D. Salisbury. College Text¬ 
book of Geology. Part II: Historical Geology, 
New edition rewritten and revised by R. T. Chamber¬ 
lin and P. Mac Clintock. H. Holt & Co., New 
York. 1930. 

Crookall, R. Coal Measure Plants, pp. 80. 40 pis. 
Edward Arnold & Co., London. 1929. 

DeCandolle, Alphonse. Origin of Cultivated Plants. 
D. Appleton Co., New York. 1898. 

Knowlton, F. H. Plants of the Past. A popular account 
of fossil plants, pp. xix, 275. 90 illus. Princeton 
University Press, Princeton. 1927. 

Noe, A. C. Pennsylvanian Flora of Northern Illinois. 
pp. 113. 45 pis. Bull. 52, Illinois State Geological 
Survey, Urbana, Illinois. 1925. 

Wells, H. C. The evidence furnished by biochemistry 
and immunology on biologic evolution. Archives 
of Pathology, vol. 9, pp. 1044-1075, May, 1930. 


128 











Dummy nM' 

9 


I 













I 










0 005 025 478 1 






























































































